Oriented connections for leadless and leaded packages

ABSTRACT

The invention discloses design concepts and means and methods that can be used for enhancing the reliability and extending the operating life of electronic devices, and assemblies incorporating such devices, and substrates and/or PCBs, especially if such assemblies are exposed to severe environments such as thermal cycling or power cycling. The main thrust of the invention is to provide flexible joints, such as columns, between the attached components, and preferably to orient such joints, so that they would present their softest bending direction towards the thermal center or fixation point of the assemblies. Joints with rectangular or elongated cross-section are preferred, and they should be oriented so that the wide face of each joint would be facing the thermal center, perpendicular to the thermal deformation ray emanating from the thermal center towards the center of each respective joint. The concepts apply equally to leadless packages as well as to leaded packages.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This present application is a NON-PROVISIONAL UTILIY PATENTAPPLICATION claiming the priority and benefits of the following sixprevious applications, which include four provisional patentapplications and two non-provisional utility patent applications, all ofwhich are incorporated herein in their entirety by reference:

[0002] 1. Provisional Patent Application Serial No. 60/231,387, filedSep. 8, 2000, entitled “Probers”, which will be referred to as Ref1, and

[0003] 2. Provisional Patent Application Serial No. 60/257,673, filedDec. 22, 2000, entitled “Probes and Sockets”, which will be referred toas Ref2, and

[0004] 3. Provisional Patent Application Serial No. 60/268,467, filedFeb. 12, 2001, entitled “Probes, Sockets, Packages & Columns”, whichwill be referred to as Ref3, and

[0005] 4. Nonprovisional Utility patent application Ser. No. 09/947,240,filed Sep. 5, 2001, entitled

[0006] 5. Nonprovisional Utility patent application Ser. No. 10/075,060,filed Feb. 11, 2002, entitled “Interconnection”, which will be referredto as Ref5.

[0007] 6. Provisional patent application Ser. No. 60/443,128, filed Jan.27, 2003, entitled “Oriented Columns & Package Leads”, which will bereferred to as Ref6.

[0008] These can be visualized easier in the following TABLE #1:

[0009] Legend for Type: PPA=Provisional Patent Application

[0010] NPUPA=Nonprovisional Utility patent application Ref# Type Ser.No. Filed on Title Ref1 PPA 60/231,387 Sep. 08, 2000 Probers Ref2 PPA60/257,673 Dec. 22, 2000 Probes and Sockets Ref3 PPA 60/268,467 Feb. 12,2001 Probes, Sockets, Packages & Columns Ref4 NPUPA 09/947,240 Sep. 05,2001 Interconnection Devices Ref5 NPUPA 10/075,060 Feb. 11, 2002Interconnection Ref6 PPA 60/443,128 Jan. 27, 2003 Oriented Columns &Package Leads

[0011] This application could also be considered a “Continuation” and/or“Continuation-In-Part” of Ref3 and Ref5.

[0012] Note:

[0013] I will refer in this application to certain pages, drawings orsketches that were included in the above References. I would like toexplain here the numbering system that was used in those references, sothat it will be clear, which page or drawing I would be referring tolater on. I will use Reference 3 to illustrate.

[0014] Reference 3 covers 4 product groups. They are Test Sockets orsimply Sockets, Wafer Probes or simply Probes, Micro-Columns or simplyColumns and Plastic Packages or simply Packages. The pages areidentified as follows. The pages of the Test Sockets are identified byTS, the Wafer Probes by WP, the Micro-Columns by MC, the PlasticPackages by PP.

[0015] Each one of these groups' documents was divided into threesections. The Specifications, the Drawings and the Additional Documents.The pages were identified as follows. The pages in the Specificationssections by S, the Drawings by D, and the Additional Documents either byAD or by A.

[0016] So for example, page 7 in the Specifications of the Micro-Columngroup would be marked thus: “MC-S-T”, i.e. MC for Micro-Column, S forSpecifications, 7 for page 7.

[0017] Ref3 and Ref5 in particular relate to the “LEADED DEVICES”covered in Group 1 in this present application.

[0018] Specific Sections in “References” that I Will Use Here:

[0019] Please review specifically the following sections in TABLE #2, inpreparation for this present application: Item Ref# Page Description&/0r Remarks 1 Ref3 PP-D-1 Radial Thermal Expansion & Contraction,showing oriented pads. 2 Ref3 PP-D-22-25 Twisted Leads, which can beattached, e.g. brazed, to the sides of leadless packages. 3 Ref3 PP-D-42Radial Thermal Expansion & Contraction-Like Item1 PP-D-1, but with“Oriented Columns” on the “Oriented Pads”. 4 Ref3 PP-D-43 A leadlesspackage, e.g. BGA, with a scattering of “oriented” connectors. 5 Ref3PP-D-44 A solder column that can be used with the above leadlesspackage, which can be then “oriented” when placed at its specificlocation, as in the above FIG. 6 Ref3 PP-D-45 Same as in PP-D-44 butwitnessed. 7 Ref3 PP-D-47 Sketch showing some oriented columns and ananchor. 8 Ref3 PP-D-75-81 Different views of the Twisted Leads forleadless packages, as shown also in Item 2 PP-D-25 above. 9 Ref3PP-D-88-95 “NAS Interplex Solder & Flux Bearing Leads”, andmodifications of same, which can be used to attach to leadless packages,and which can be “oriented” as per invention. 10 Ref3 PP-D-97-98 Moremodifications to provide leadless packages with oriented leads. 11 Ref3PP-D-104-105 Show how the contact pads on substrates can be modified tobe adapted to leads that are oriented. 12 Ref3 PP-AD-42 Like in Item 2PP-D-25, but witnessed. 13 Ref3 PP-AD-43 Sketch showing a variation onwhat is shown in Items 4-6 PP-D-43-45 and Item 7 PP-D-47 14 Ref3PP-AD-48 As in Item 8 PP-D-75, but with reverse twist and witnessed. 15Ref3 PP-AD-62 Another view of the FIG. in Item 2 PP-D-22 but witnessed.16 Ref3 PP-AD-63 Another view of the FIG. in Item 2 PP-D-23 butwitnessed. 17 Ref3 PP-AD-64 As in Item 2 PP-D-24, but witnessed. 18 Ref3PP-AD-65 As in Item 2 PP-D-25, but witnessed. 19 Ref3 PP-AD-66 Anothercopy of Item 3 PP-D-42. 20 Ref3 MC-AD- A copy of an article on “RibbonBonding”, with pictures of bonded 108-113 ribbons in pagesMC-AD-110-112. 21 Ref3 Misc Several Sections in the text description

Oriented Connections For Leadless and Leaded Packages

[0020] Additional Special References:

[0021] In addition, the following references relate to both groups ofproducts covered by this present application, i.e. the “Leaded Devices”as well as the “Leadless Devices”.

[0022] I would like to incorporate here the three following papers,which I had attached at the end of Ref6, as appendices to that document,and were numbered as “Additional Documents”.

[0023] Ref7. Paper #1—“Improving Reliability of Plastic Packages”. Thiswas included in Ref6, pages OC-A-36 through -42.

[0024] Ref8. Paper #2—“BGA Mounting and Chip Scale Packaging”. This wasincluded in Ref6, pages OC-A43 through -49.

[0025] Ref9. Paper #3—“BGA Mounting Using Improved Solder Columns”. Thiswas included in Ref6, pages OC-A-50 through -56.

[0026] Papers #1 & #2 were intended to be published at the “EighthAnnual Pan Pacific Microelectronics Symposium 2003”, SMTA, Kohala Coast,Island of Hawaii Hi., Feb. 18-20, 2003. This conference is organized bythe SMTA (Surface Mount Technology Association), 5200 Wilson Road, Suite215, Edina, Minn. 55424-1343, Tel: 952-920-7682; Fax: 952-926-1819;E-Mail: smta@smta.org, www: www.smta.org. However, because of financialdifficulties, I cancelled my attendance and withdrew the papers from theconference. However, the papers as intended to be presented, wereincluded in Ref6.

[0027] Paper #3 was presented at the “IPC Printed Circuits EXPO 2003”,IPC, Long Beach, Calif., Mar. 25-27, 2003. This conference is organizedby the IPC, Lincolnwood, Ill., Tel: 847-790-5325.

[0028] I would also like to refer to the following paper, which I hadpresented in connection with my old CCMD/Solder Columns, which I haddeveloped around 1982-86.

[0029] Ref10. Paper #4—“New Solder Column Alloy Improves Reliability ofChip Carrier Assemblies”, by Gabe Cherian, Craig Wynn and Harry White,Raychem Corporation, Menlo Park, Calif., 18^(th) International SAMPETechnical Conference “Materials For Space—The Gathering Momentum”,Society for the Advancement of Material and Process Engineering (SAMPE),Seattle, Wash., Oct. 7-9, 1986, pp. 1056-1070. I will be referred tothis paper as Ref10.

[0030] This paper shows that a solder column that has a wide base nearthe pads and a narrower waist about the middle of the height is bettersuited to withstand the ill effect of the TCE Mismatch between thepackage and the substrate. The amount of flexing and the level ofbending stresses become more favorable with this kind of general shape,than with a column that is uniform in cross section throughout its wholelength. I would like to refer to such a shape as the “starved” columnshape. I will talk more about that further down below.

[0031] Furthermore, I will refer in the present specification to thefollowing articles and patents.

[0032] Other Articles:

[0033] Ref11. Paper #5—Ken Inaba, John Heffernan, and Dr. DominiqueNumakura, “Zero Clearance Soldermask for High-Density SMT”, PC FABMagazine, January 2003, pp. 18-21.

[0034] Ref12. Paper #6—Larry Gilg, and Chris Windsor, “Die Products:Ideal IC Packaging For Demanding Applications”, Electronic DesignMagazine, Dec. 23, 2002, pp. 47-48.

[0035] Ref13. Paper #7—John H. Lau and Katrina Liu, “Global Trends inLead-Free Soldering”, Advanced Packaging Magazine, January 2004,pp.27-30.

[0036] Other Patents:

[0037] Ref14. U.S. Pat. No. 4,655,382, dated Apr. 7, 1987, entitled“MATERIALS FOR USE IN FORMING ELECTRONIC INTERCONNECT”; Inventors:Geoffrey B. Wong and Arthur W. Lopez, Jr.; Assignee: Raychem Corp.,Menlo Park, Calif.

[0038] Ref15. U.S. Pat. No. 4,664,309, dated May 12, 1987, entitled“CHIP MOUNTING DEVICE”; Inventors: Leslie J. Allen, Gabe Cherian andStephen H. Diaz; Assignee: Raychem Corp., Menlo Park, Calif.

[0039] Ref16. U.S. Pat. No. 4,705,205, dated Nov. 10, 1987, entitled“CHIP CARRIER MOUNTING DEVICE”; Inventors: Leslie J. Allen, Gabe Cherianand Stephen H. Diaz; Assignee: Raychem Corp., Menlo Park, Calif.

PAGES 11 THROUGH 13 LEFT OUT INTENTIONALLY STATEMENT REGARDING FEDERALLYSPONSORED RESEARCH OR DEVELOPMENT

[0040] Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

[0041] Not Applicable

GENERAL BACKGROUND OF THE INVENTION

[0042] 1. Field of the Invention

[0043] The present invention relates generally to means and methods forattaching devices to each other, more particularly to attachingelectronic devices and packages on to each other, or on to substrates orPrinted Circuit Boards (PCBs), etc. The invention relates to bothleadless packages, such as BGAs or LCCCs, as well as to leaded packages,such as DIPs.

[0044] The invention further relates to the reliability and longoperating life of assemblies incorporating such devices, and morespecifically, when such assemblies are exposed to harsh operating orenvironmental conditions, such as power cycling or thermal cycling, andmore specifically yet, when the different components of such assemblieshave different Thermal Coefficients of Expansion (TCEs), what isreferred to TCE Mismatch.

[0045] Furthermore, the invention relates to the connecting means, suchas leads, legs, solder joints and the like, both for the leadless aswell as the leaded devices, and the shape and orientation/positioning ofthese connecting means, especially as to how all this would affect thereliability and long operating life of such assemblies, especially whenexposed to the above mentioned operating conditions.

[0046] Introduction:

[0047] The products covered by this present application can be dividedinto two groups. The first group includes any leadless devices, such asBall Grid Array Packages (BGAs), Leadless Ceramic Chip Carriers (LCCCs)or any other leadless packages. The second group includes any leadeddevices, such as Dual-In-Line Packages (DIPs), or any other leadedpackages.

[0048] I will first provide a general introduction and backgroundapplicable to both groups of products, and then another one, moreexpanded, applicable to each of the two groups of products separately.

[0049] Note: The examiner may decide that both groups of products are sorelated, that they can be processed as one application. However, if theexaminer decides that they should be divided into two separateapplications, then I would abide by that decision. Please advise.

[0050] 2. Prior Art

[0051] In my opinion, there is nothing in the Prior Art that resemblesthe concepts covered by this present invention.

[0052] The only thing that could be considered prior art is what hasbeen covered in my prior applications, i.e. in Ref1 through Ref6, whichwere cited/listed in the cross-reference section at the beginning of theapplication. However, this present application is either a continuationor a continuation-in-part to those references.

[0053] Objective

[0054] The main object of this invention is to improve and enhance thereliability and long operating life of assemblies incorporating leadlessand/or leaded devices, especially when such devices are mounted on orattached to each other or to substrates or Printed Circuit Boards(PCBs), and more specifically, when such assemblies are exposed to harshoperating or environmental conditions, such as power cycling or thermalcycling and more specifically yet, when the different components of suchassemblies have different Thermal Coefficients of Expansion (TCEs) [TCEmismatch].

[0055] The reliability issues can be divided into several differentgroups. The most talked about issue is with surface to surfaceinterconnections/mounting, and is the fact that the solder joints maycrack and/or delaminate from the solder pads and end up with opencircuits.

[0056] There are however, a number of other problems that impair thereliability.

[0057] One new reliability issue is related to the new “lead-free”solders that are being mandated to be used soon, to avoid problemsrelated to solders containing lead (Pb). A new fact is starting to getheard about these new lead-free solders. It seems that there may beproblems with the copper solder pads delaminating from the PrintedCircuit Board (PCB) during the reflow/mounting process, or at leastgetting weaker. See Ref13 above.

[0058] So, if this is true, then the concepts presented in this presentinvention will improve the reliability of such assemblies as well,because they will reduce the stresses on the pads, and hence less chancefor them to delaminate or to fail prematurely.

BACKGROUND INFORMATION

[0059] It has been known in the industry that when two bodies areattached together, like in the case of a leadless electronic packagemounted to a PCB, and the assembly is exposed to harsh environmentalconditions, such as power cycling or thermal cycling, the joints betweenthe two bodies can get overstressed and may fail prematurely. It hasalso been know/shown that if the joints are elongated, like columns orleads or legs, instead of being wide, short, or stubby connections, thenthe life expectancy of such assemblies gets extended.

[0060] Furthermore, it was mentioned in the previous referencedapplications, especially in Ref3, as well as in Ref5, that “OrientedLeads” or “Columns” can improve the life and reliability of assembliesincorporating packages and substrates, especially if the components havesome TCE mismatch, and if they are exposed to temperature fluctuations.I have also provided some sketches and drawings illustrating what Imean, as listed in Table 2 above.

[0061] Ref3, and especially Ref5, include a lot of descriptions andexplanations about “orienting” the leads, so that they would face thethermal center or thermal fixation point of the packages, or rather ofthe assemblies. I will refer to the explanations given in those citedreferences and will not repeat the explanations here.

[0062] I had also shown, in those references, a number of ways toachieve the desired designs and goals.

[0063] One method was to use a flat leadframe with the leg blanksoriented and radiating out directly from the plastic body, i.e. comingout of the plastic body, not in a direction that is perpendicular to thesides of the body, but at an angle in the correct, more desirable radialdirection. The drawings were small and may have not been able to conveymany of the details. I will show here in this specification somedrawings that will clarify that embodiment.

[0064] However, I have shown in Ref6, another way of achieving the sameend goal, but where the individual legs or leg blanks would firstprotrude out from the package body in an orthogonal direction, i.e.similar to the present “conventional” way, and then each “leg blank”would curve, while still flat, a certain part of a circle and then endup in a special desired direction for each specific leg, as will beexplained in the following specifications

[0065] In the following pages, I will include and describe someadditional examples of how we can capitalize on this theory; i.e. usingoriented leads or columns.

BRIEF DESCRIPTION OF THE INVENTION

[0066] The invention can basically be described simply by saying that itproposes to observe two specific things when attaching two bodies orcomponents together, especially when the bodies are expected to beexposed to harsh environmental conditions.

[0067] 1. Make the connecting elements, which will join the two bodiestogether, to have some flexibility, to allow and/or compensate fordimensional variations between the two bodies, e.g. from thermalexpansion or contraction. One example is to make the joints like tallcolumns, i.e. slender, elongated, and possibly curvilinear, elements,ideally situated at a generally perpendicular angle to the generalsurface of the bodies. We would refer to them as “columns”. The columnswould act as “flexible joints”, and will provide for a way to compensatefor the deformation of the bodies under the prevailing conditions. Note:If the dimensional variations are expected to be in more than onedirection, then the flex joints should be able to compensate for thesevariations in all their directions. Hence the flex joints should be ableto flex in all the respective directions. This is why these joints couldbe curvilinear, to have more than one degree of freedom, yet to bestrong enough to still retain the bodies together as required.

[0068] 2. If the cross-section of these columns is not round or square,then orient the columns, so that they would provide the least resistanceto flexing. For example, if the columns would have an oblong orelongated or rectangular cross-section that is generally longer than itswidth, or in other words, has a long axis and a short axis, then thesecolumns would be oriented so that their wider surfaces would be facinggenerally in the direction toward the thermal center or the fixationpoint of the package or the assembly. We can also rephrase that bysaying that each column would be oriented such that the short axis ofits cross-section would be in a direction of its respective thermaldeformation ray, which would be emanating from the thermal center of thepackage, or from the fixation point of the package, and going to thecenter of the cross-section of each column.

[0069] In addition, some variations in the shape and construction of thecolumns are covered by the present invention, as will be describedbelow, together with some additional features.

[0070] The main object of the invention is to mount such devices,especially electronic packages, on their substrates, using specialconnecting means, hereinafter referred to as Oriented Connections, so asto improve the performance life and/or reliability of such assemblies,especially with respect of Power Cycling, Thermal Cycling (columns)and/or Shock and Vibration (columns & anchor).

[0071] The connecting means would generally be situated between thedevice and the substrate. They would be situated with the general axisof their elongated body to be generally perpendicular to the generalsurfaces of the device and the substrate. The connecting means wouldalso have their cross-section, normal to their body axis, such that thecross-section would be elongated, or oblong, or rectangular.

[0072] Oriented Connections are connecting means, which have anelongated cross-section, whether rectangular, or oblong or any othershape, where the cross-section has one large dimension or length and ashorter dimension, generally perpendicular to the first one, or width.Consequently, we can say that the cross-section would have one long axisand one short axis perpendicular to the long axis.

[0073] These connecting means would be oriented such that the short axisof the cross-section would be in line with, or approximately in linewith, a thermal deformation ray, which emanates from the thermal center,or fixation point of the device, and which radiate towards the center ornear the center of the cross-section of the connecting means.

[0074] The invention will also show at least two or more ways of shapingthe legs/leg blanks of leaded packages in a certain specific way foreach individual leg of these packages. This can be accomplished bytwisting the legs or by shaping the leg blank in such a way that asimple folding operation would accomplish the same end result.

[0075] In the case of leaded packages, most of the legs, in Ref3 andRef5, were twisted to orient them as desired. In a few cases, the legswere not twisted, but were “folded”. See Ref5, FIGS. 20 through 22,FIGS. 25 and 26, and FIGS. 32 through 40, as well as in Ref3, pagesPP-D-5 and 6, 82 through 87, 99 and 100, and pages PP-AD-45 and 46. ThisInvention will provide more examples of leaded plastic packages with“oriented” legs, without twisting the legs. It will also give moreexamples of solder pads, which could accept both the conventionalpackage legs as well as the new proposed package legs, which were shownin Ref3, pages PP-D-104 and 105, as well as in Ref5, FIGS. 23 and 24.

[0076] In the case of leadless packages, the invention will expand onthe concepts shown in Ref3, pages PP-D-1, 42, and PP-AD-66, as well asmany of the concepts described in Ref5, under the group of “leaded”packages.

[0077] The Invention provides means and methods of accomplishing theabove goals and objectives.

[0078] As mentioned above, the application covers two groups of devices,the leadless and the leaded devices.

[0079] I will first describe the embodiments for the leadless devicesand then those of the leaded devices.

[0080] Definitions

[0081] Vertical, Horizontal, etc.

[0082] When we talk about packages or the like being mounted on PrintedCircuit Board (PCB) or substrates or the like, we most of the time,visualize that the PCB is laying on a horizontal table, and that thepackage is being mounted to it, where the body of the package isparallel to the PCB. Hence, we say the PCG and the package arehorizontal. If the package is leaded, we then say that the legs of thepackage are vertical. If the package is leadless, but we want to providecolumns between the package and the PCB, then we say that the columnswill be vertical, figuring that they will be perpendicular to thegeneral package body direction and/or to the PCB general position.

[0083] Usually, the legs of leaded packages are made of flat sheetmetal, blanked and formed, etc. The legs are vertical, and the legs axesare also vertical. We kind of ignore the part of the legs that is closeto the package body and that is still horizontal.

[0084] Usually the legs cross section is rectangular, where the width ofthe rectangle is the thickness of the sheet metal and the length of therectangular is several times larger than its width.

[0085] We also talk about the face of the leg, or the wide face of theleg, which is the side of the leg formed by the length of the crosssection rectangle. I will refer to this face of the leg and state thatit should face the thermal center of the package or of the assembly. Itis as if a person is standing inside the leg, and facing in thatdirection.

[0086] Thermal Deformation:

[0087] When a body is at room temperature or at any initial temperature,and then it gets heated or cooled, it expands or contracts respectively.The changes in its dimensions correspond to the amount of temperaturechange and to the dimensions of the body. They also correspond to theThermal Coefficient of Expansion (TCE) of the body's material. Thesechanges in dimensions will be referred to hereinafter as “ThermalDeformation”.

[0088] Thermal Center

[0089] FIGS. 4 and 5 in R5, drawings sheets 4/72 and 5/72, illustratethe concept of the “thermal center”. If a package is heated or cooled,then the body of the package will expand or contract, and every pointon/in the body will move along a certain line or “ray”, in a directionof the lines shown in the figures. Each of these lines or rays has 2ends, obviously. One end is at the individual point of the body beingconsidered, and the other end is at some fixed point in the body. If thepoint of the body is fixed or anchored at a certain point in space, thenthis fixation point will be the other end of that line or ray. I willrefer to such lines, as the “thermal deformation rays”, or simply“rays”. I will refer to that fixed point as the “thermal fixation pointor center”.

[0090] If, on the other hand, the package is not fixed at any specificpoint, but is simply attached to another body via the leads, legs orsolder joints, which are evenly distributed along the body, then we cansay that the package is “floating”. In this case, we can consider thatthe geometric center of the package is its “thermal center”. This ofcourse assumes that the package is homogeneous, and that all itselements are equal and symmetrical and balanced. It also assumes thatall the joints are approximately equally strong or stiff and equallydistributed around on the package. So, in such as case, all the thermaldeformation rays will start at the geometrical center of the package,which will be considered to be its “thermal center” as well, and therays will emanate from that center and go in a direction towards anyspecific point under consideration.

[0091] There will be other definitions that will be introduced duringthe course of describing the invention. In most cases, I will try tohighlight the fact that these are new definitions.

PREAMBLE TO DETAILED DESCRIPTION

[0092] While the invention is susceptible of various modifications andalternative constructions, certain illustrated embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form disclosed, but, on the contrary, theinvention is to cover all modifications, alternative constructions, andequivalents falling within the spirit and scope of the invention asdefined in the claims.

[0093] While I am describing the drawing in more details, I will at thesame time explain the technology basis of the invention, wheneverapplicable. I will also include a number of examples in this section,which should be considered as part of the embodiments for the purpose ofthis application as well.

[0094] This description covers more than one invention. The inventionsare based partly on the same technology platform, but then each of theinventions has some additional features of its own. Not being an expertin handling patents, I would like to leave it to the patent examiner todecide on the number of the inventions contained and how to split oneinvention from the other.

[0095] I will also cover in this application a number of embodiments forsome of the described inventions. Some will relate to the legs of thepackages, others will relate to the solder pads, which are part of thePCB or substrates or other devices, and which are to accept the legs ofthe above packages.

[0096] I will then describe each of the other applications separately.

[0097] Finally, I will describe some new features that are common tomany applications.

[0098] Moreover, I will describe some additional features, related tosome individual applications. These new features are not based on thecommon basic technology that I started with at the beginning.

BRIEF DESCRIPTION OF THE DRAWINGS

[0099] The drawings can be grouped into two separate groups. The firstgroup includes FIGS. 1 through 35 and relates to leadless packages. Thesecond group includes FIGS. 36 through 92 and relates to leadedpackages.

[0100]FIGS. 1 through 3 show prior art leadless packages, highlightingthe shape of their solder pads.

[0101]FIGS. 4 through 6 show the basis of the concepts presented in thisinvention, namely to make the solder pads elongated or rectangular andto orient the pads so that they face the thermal center or the fixationpoint of the package and/or the assembly.

[0102]FIGS. 7 through 9 show an LCCC with solder columns, on top of therectangular solder pads, highlighting the fact that the columns are tallrectangular in cross section, and that their wide faces are orientedtowards the thermal center of the package.

[0103]FIGS. 10 through 13 show a BGA, with several concentric rows ofsolder pads/joints/columns, according to the present invention, i.e.tall columns, with rectangular cross section and oriented to face thethermal center of the package.

[0104]FIGS. 14 through 16 show an LCCC with solder balls applied to itsrectangular oriented solder pads.

[0105]FIGS. 17 through 25 show the process of reflowing the solder ballsshown above and viewing how they would change from spherical balls totall rectangular columns and then to “starved columns”. All the while,of course, keeping their orientations as per present invention.

[0106]FIGS. 26 and 27 show a strange set of figures. They illustrate therelation between the solder balls, the vertical rectangular columns andthe starved columns, and how they sit on top of rectangular solder pads.FIG. 26 shows the figures in “wire form” format, while FIG. 27 in “hide”format.

[0107]FIG. 28 shows some nomenclature to help visualize the meaning ofsome terms used in the specifications.

[0108]FIG. 29 shows the concept of using solder balls with a specialcore, which can act as a spacer.

[0109]FIG. 30 shows an analysis of two different methods of usingpreforms. The top set of figures show what would happen if we do not useany spacers or stand-offs, while the bottom set shows the effect ofusing some spacers or stand-offs.

[0110]FIGS. 31 through 33 show a device that can be used to lift a BGAabove the PCB during the reflow process, to stretch the solder jointsand to create the rectangular columns and/or the starved solder joints.

[0111]FIG. 34 shows the concept of using two wires to simulate theeffect of a tall wide column with a rectangular cross section.

[0112]FIG. 35 shows the concept of creating or growing a tallrectangular solder column and the mask that could be used to do that.

[0113]FIGS. 36 through 44 show a standard conventional leaded package(Prior Art) and some details of how such a package is manufactured andmounted on solder pads on a PCB. These drawings are here just to be ableto compare and to visualize the differences between the state of the artand the new concepts presented in the present invention.

[0114]FIGS. 45 through 47 show a new leadframe, as per presentinvention, and compares it against the state of the art leadframe.

[0115]FIGS. 48 through 54 show the manufacturing steps used to work withthe new leadframe, so as to end up with the new leaded package, as perpresent invention. The new package has it legs oriented, such that the“legs columns” are oriented to face the thermal center of the package,and eventually the thermal center of the assembly of this package on asubstrate or a PCB.

[0116]FIGS. 55 through 58 show additional view of the end resultpackage. Just to better visualize how the legs are formed in theproposed orientation.

[0117]FIG. 59 shows a summary view of the important steps used tomanufacture a package as proposed.

[0118]FIGS. 60 and 61 show the new leadframe at two important stages ofits manufacturing, and compares them with the views in FIGS. 39 and 40.

[0119]FIGS. 62 through 64 show different solder pads that can be usedwith the proposed packages. FIG. 62 shows the standard conventionalpads, while FIG. 63 shows the “dedicated” pads, and FIG. 64 shows the“combo” pads.

[0120]FIG. 65 shows a package with oriented legs, sitting on top of“dedicated” solder pads.

[0121]FIGS. 66 through 70 show a package with oriented legs, sitting ontop of “combo” pads. Views from different viewpoints are shown, to helpvisualize the concept.

[0122]FIGS. 71 and 77 show a pair of legs on one individual pad in eachof the figures. The idea here is to show that both the standardconventional state of the art packages can fit and work on the “combo”pads, as well as the new packages, with oriented legs, as per presentinvention.

[0123]FIGS. 78 through 81 show four different views of another newpackage, with oriented legs too, but where the leadframe is differentthan the one in the previous figures.

[0124] The lead frame in the earlier figures, FIGS. 36 through 77, iswhat I refer to as the “Oriented” leadframe. The one used in this groupof figures, FIGS. 78 through 92, is what I refer to as the“Orthogonal-Oriented” leadframe. The difference is the way the legblanks exit from the package body. In the “Oriented” leadframe, the legblank exit on some angle to the body sides or centerlines, while in the“Orthogonal-Oriented” leadframe, the leg blank first exit in aperpendicular direction to the body sides or centerlines, and then theleg blanks have a “neck” that curves and ends up in a direction that is“oriented” as required by the present invention. So, both leadframes endup with “oriented” legs, but in one leadframe, the leg blanks emergefrom the body in the “oriented” direction, and in the other leadframe,the legs start at a normal angle and then become oriented later.

[0125] Please note that a combination of the two leadframes directionsis part of this invention too. In other words, the “orthogonal-oriented”version, can have the leg blanks emerge from the body at some angle,which is neither the ultimate oriented angle, nor the normal,perpendicular direction, but something in between, and then the neckwould curve properly to end up with the legs oriented properly at theend.

[0126]FIGS. 82 and 83 show the new package mounted on a PCB, where thesolder tails of the legs have been inserted into through-holes in thePCB for clinching and soldering.

[0127]FIGS. 84 and 85 show the leadframe according to the new method,i.e. the “Orthogonal-Oriented” method.

[0128]FIGS. 86 through 90 show the leadframe, with the package body onit already, at different stages of the manufacturing process.

[0129]FIG. 91 shows the leadframe, as if it has gone through all themanufacturing steps leading to the condition shown in the above figures,except that the package body has been removed. This is just forclarification and visualization. The carrier strip is still present.

[0130]FIG. 92 shows a 3-D view of the same leadframe shown in the abovefigure, with the oriented legs, but without the carrier strip.

PAGES 38 THROUGH 40 LEFT OUT INENTIONALLY SPECIFIC BACKGROUND—LEADLESS

[0131] Note to the Examiner:

[0132] All the information in this section was part of Ref6, which wasincorporated in this application by reference at the beginning of theapplication. I could simply refer the reader to the text in that Ref6and not repeat it here. This would reduce the size of this “formal”application. Please advise. Also, although I have copied all the texthere from Ref6, I have not included the figures. I simply mentioned thefigures, as being figures in Ref6. I hope that this is correct andacceptable. However, if Examiner desires, I could very easily includeeither all or a few of those figures here in this specification as well.

[0133] Please advise.

[0134] Review of Some “Natural Phenomena”

[0135] Basically, most of the information in this section could beconsidered as part of “Material Science” or “Metallurgy” or “Physics”.Probably no new information for most of the readers. It is here simplyto describe certain physical phenomena and to highlight certainobservations and to help in understanding and accepting the conceptspresented in the present invention.

[0136] Standard Conventional Solder Pads

[0137] Standard conventional leadless packages, e.g. Ball Grid Arrays(BGA) or Leadless Ceramic Chip Carriers (LCCC) have solder pads that areeither rectangular, square or round (circular) in shape. Theirdimensions are usually covered by JEDEC Standards or the like.

[0138] So far, all such packages have been either square or rectangular,where their two main central axes are orthogonal, i.e. perpendicular toeach other, and the sides of the packages are straight and parallel tothe central axes. The solder pads also have always been ORTHOGONAL intheir location and/or shape, as well. By this I mean that the solderpads are laid out along rows and columns that are orthogonal andparallel to the central axes and sides of the package body. Examples ofsuch packages are the BGAs and LCCCs mentioned above. It is alsoimportant to notice that when the pads are not round, i.e. when they aresquare or rectangular, then the pads sides also are orthogonal andparallel to the sides and central axes of the package.

[0139] How the Shape of the Solder Pad Affects the Shape of the SolderJoint

[0140] Another basis for the proposals in this invention is the factthat in general a solder joint usually follows or imitates the shape ofthe solder pad, which it is attached to. Another thing is that thedistance between the two pads that are being attached together, most ofthe time, one pad on top of the other, and the amount of solder presentat the joint to start with, also affect the shape of the solder joint.

[0141] I will first explain what I mean by that and then show how we cantake advantage of this phenomenon to create the kind of solder jointsthat would work best for us.

[0142] To do that, I will use two cases. Case I is where we have onesolder pad, with some solder molten and reflown on top of this pad.Then, Case 2 is where we have two solder pads being joined together witha certain amount of solder between them and with a certain distancebetween the pads.

[0143] Note to the reader: Most of the text in this section had beenincluded in Ref6. Ref6 has also a number of figures that go along withthis text. I will not duplicate those figures here in this application.I would rather like to refer the reader to those figures in Ref6.

[0144] CASE 1: One Solder Pad with Solder on Top of it.

[0145] First, the effect of the shape of the solder pad.

[0146] Solder is well known for its high surface tension and its strongcapillary characteristic and its affinity to wet to surfaces ofmaterials that are wettable to it. Of course, this happens when thesolder is molten and is free to move around, and when the wettablesurfaces are also hot enough and clean as well, so that the solder wouldnot freeze and would adhere to those surfaces. As a result, when we havea proper amount of solder and reflow it on top of a pad made of solderwettable material, like copper, then the molten solder will spread onthe surface of the pad and create a layer of solder on the surface ofthe pad. Of course the solder pad itself should also be hot enough andup to the proper temperature, and should be clean as well.

[0147] Second, the available amount of solder will affect the shape ofthe solder on top of the pad.

[0148] If the amount of solder is enough, then the solder will cover thewhole surface of the pad. If there is still enough solder, then we willsee a “pillow” of solder, with the pad as its base and a “dome” formedon top of the pad. The height of the dome will depend on the availableamount of solder. The edges of the dome will be touching the edges ofthe pad. If the pad is round, then the pillow will have a round base,too. If the pad is rectangular, then the pillow's base will berectangular exactly like the pad (see Ref6, Fig. B-6, sketch #9, (NotShown), which I will talk more about later), and if the pad is irregularin shape, then the base of the pillow will have a correspondingirregular shape similar to that of the pad (as in Ref6, Fig. B-7, sketch#G. (Not Shown), which I will talk more about later also).

[0149] Example, or case in point.

[0150] Ref11, which is the Article that was attached as part of Ref6,pages OC-A-06 through -11, “Zero Clearance . . . , showed in its FIG. 4,page OC-A-09, some solder pads that are covered with solder masks. Themask in the Left Hand Side (LHS) picture does not completely cover the“neck” or “tail” of the solder pads, which is the part of the coppertrace that connects the different pads together. The picture on theRight Hand Side (RHS) shows the better solder mask, which does not leaveany part of the neck exposed. The article is touting this new soldermask technique for other reasons, but this new technique (RHS) hasanother advantage. It produces a “balanced” solder joint.

[0151] One of my business associates, and let's call him Bill, wastelling me about a problem they had when they solder reflowed their BGAson their Substrates. Some of the solder pads had “necks” as shown in theRHS picture of the above article. Bill was saying that the solder jointsthat had these necks were distorted in shape. They were not round asthey were supposed to, but had a shape that followed roughly the shapeof the pad with the neck. And the joints were “pulling” sideways. So inorder to compensate for that, Bill put an additional (fake or idle) neckon the opposite side of the existing neck, to balance out the solderjoint. This gave me one hint for my proposed designs here.

[0152] My Ref6, Figs. A-1 through A-4. (Not Shown), illustrate theconcept in some more detail. Ref6, Fig. A-1 shows three solder padsconnected together by “necks”, as in the figures of the articlementioned above. I have drawn on one of the pads a solder joint, roughlyas Bill had described it to me. Ref6, Fig. A-2 shows an illustration ofa board with two solder pads, with a neck connecting them. A solder maskcovers the board, leaving an opening around each of the solder pads. Theopen circle in the mask is too large and leaves a certain portion of theneck exposed, as seen in the figure. Ref6, Fig. A-3 shows the shape ofthe solder joint, connecting two boards or two components, having solderpads with similar necks, e.g. a BGA on top of a board. Here I am notshowing the top pad. (I will talk more about joining two components,further down below). The joint here would have a protrusion, which Iwill refer to as the “neck knob”. Ref6, Fig. A-4 shows the cross sectionof the solder joint at different elevations. The top and bottom sketchshows the cross section near the pads, while the middle sketch shows thecross section near the middle of the height of the joint. You can seethat the middle section is more rounded and the neck knob is not aspronounced, not as “angular”, as in the two other cross sections. Thetop and bottom sections are influenced heavily by the shape of the pads,while the middle section is less influenced by them and so the highsurface tension of the solder takes over and tries to smoothen out theshape of the column and to make the cross section more uniform and moreround.

[0153] Second, the Amount of Solder,

[0154] If we keep increasing the amount of solder, that will be reflownover the pad, then we will notice the following progression of events.

[0155] First, with just barely enough solder to cover the surface of thepad, and assuming that there is enough to cover the whole surface of thepad, then the solder pillow will be very thin and not tall at all. Theedges of the pillow will show a slight small wetting angle, that is theangle between the surface of the pad and the outer upper surface of thepillow will be only a few degrees, say 5 degrees for argument's sake.

[0156] Then, if we add more solder to the pillow and while the solder isstill molten, then the pillow will increase in height or thickness. Wewill also notice that the wetting angle will increase. It can become 15degrees.

[0157] By adding more solder and keeping it molten, then the pillow willbecome fatter and higher, but its edges of its base, which is touchingthe pad, will still be confined to the shape of the pad. The wettingangle will become larger, until it would reach a 90 degrees angle. Herewe can say that the pillow's edges are vertical and stay vertical for acertain height and then taper down inwards to the center of the pillowso that at the center the surface of the pillow is horizontal again, asexpected. Assuming that the pad is horizontal.

[0158] If we add more solder yet, then the wetting angle would be largerthan 90 degrees. This means that the solder pillow will become largerthan its base. The base of the pillow will still have the same shape ofthe pad, but the pillow will have a “belly” that bulges out beyond thepad. We can say that its “footprint” has become larger than its base.

[0159] If we keep adding more solder, then we may reach a point wherethe solder may form a solder ball. The ball may still have a base thatresembles the shape of the pad, but gradually the ball would become morelike a sphere.

[0160] If the pad is round, then the solder ball will keep its truespherical shape or pretty close to it. If the pad had a different shape,other than round, say like a rectangle, then the solder pillow willstart as a rectangular base, and then when it reaches the proportions ofa ball, then the ball would be more oblong, like a watermelon say.

[0161] CASE 2: Two Solder Pads, Being Joined Together. (One on Top ofthe Other). See Ref6, FIGS. B-1 through B-7.

[0162] First, the Shape of the Pads.

[0163] We can start by having both pads having the same shape. Thesolder, when molten, will wet the bottom pad and try to cover its wholesurface. When that is accomplished and if the amount of solder isappropriate and if the solder had already reached and touched the toppad, then it will wet to the top pad as well and will try to have theshape of the top pad as well.

[0164] If the volume of solder is correct, then the solder joint betweenthe two pads will have its edge walls almost vertical and straight. Ifboth pads were round, then the solder joint would look like a perfectuniform round disk. See Ref6, Fig. B-1. If the pads were square, thenthe solder joint would look like a perfect square block. See Ref6, Fig.B-2. If the pads were rectangular, then the solder joint would be like aperfect prism or parallelepiped. See Ref6, Fig. B-3.

[0165] Second, the Distance or Gap between the two Pads.

[0166] The height of the solder joint will be affected by a number offactors. If the vertical distance between the pads is controlled by someexternal means, e.g. a mechanical fixture or a solid metal ball placedbetween the two components to act as a spacer, then the volume of thesolder joint should correspond to the space between the two pads, whichwould be proscribed by (equal to) the surface areas of any of the twopads times the distance between the two pads.

[0167] If on the other hand, there is no mechanical fixturing holdingthe space fixed and constant, then probably the weight of the topcomponent will affect the final distance between the pads. There will bea balance between the weight (pushing downwards) and the surface tensionof the molten solder (trying to keep the solder shape more as a ball,thus pushing upwards) to come up with some case of equilibrium. Theresult could be that, even for the ideal volume of solder, we would geta shorter joint which would bulge out more or less depending on themagnitude of the top weight pushing downwards on top of the solderjoint.

[0168] Let us dream here for a moment.

[0169] Suppose again that we are starting with the ideal volume ofsolder, and that we are using a fixture to control the space between thetwo pads. When the solder is molten and the solder has wetted bothbottom and top pads, then we move and adjust the distance between thetop pad with respect to the lower one. If the distance between the padsis correct and just right, then the edge walls of the solder joint willbe fairly vertical and the solder joint would be “uniform” in crosssection. Now suppose that the fixture moves and brings the top pad downa small amount. We would see that the solder joint would bulge out asdescribed above. The cross section at the belly will be larger than ateither top or bottom pad. Of course this has to happen while the solderis still molten and has to be done very carefully so as not to disturbthe joint too badly and break it open. Now suppose we do the opposite.We let the fixture raise/lift the top pad away from the bottom pad. Oncewe go above and beyond the “correct/ideal” height, then we would noticethat the solder joint would become thinner at the middle of its height.I suppose that it is relatively clear to the reader that by controllingthe height or distance between the top and the bottom pad, we cancontrol the shape of the solder joint. The larger the distance betweenthe pads, the slimmer the joint. The size of the cross section near themiddle of the solder height would vary inversely with the distancebetween the pads. That is of course assuming that we do not change theoriginal volume of the solder at the joint, and assuming of course thatall this is done while the solder is still molten and it is all donevery carefully and without too much shaking and without disturbing thesolder so much as to break the joint.

[0170] I believe that the reader can visualize all this, and that thiswhole thing is feasible.

[0171] Starved Solder Columns

[0172] The following set/group of figures/drawings marked B show varioussets of pads and each set consists of a pair of such pads but at adifferent distance for each pair. The amount/volume of solder in eachcase is supposed to be the same and constant. The idea here is to showhow we could control the shape of the solder “column” so as to achievecertain goals.

[0173] I will show how we could obtain solder columns that are moreflexible under bending and that would enhance the operating life of theassembly, as compared to the conventional Solder Balls that are popularin the market nowadays.

[0174] Now, Let's go to the Group of Drawings Marked B.

[0175] Ref6, FIG. B-1, (Not Shown), shows three pairs of round solderpads, each pair consisting of one pad on top of another, with a certaindistance (gap) between the two pads. I have marked the pairs as #4, 5and 6. The distance (gap) between the pads in sketch #4 is small, thedistance in

[0176] sketch #5 is larger and the distance in sketch #6 is still largeryet. Assuming that we do not change the volume of solder between thepads, then it is clear that the joint will be skinnier (smaller diameterat the belly) the higher the distance (gap) between the pads.

[0177] Ref6, Fig. B-2 shows a similar arrangement, but with square pads.Again, the sketches try to illustrate that the solder joints will beskinnier when we increase the distance (gap) between the pads.

[0178] Ref6, Fig. B-3 again shows a similar arrangement, but withrectangular pads. Again, the sketches try to illustrate the same fact,that if the pads are pulled out away from each other, the joint willbecome skinnier the larger the distance (gap) between the pads.

[0179] Here I am also showing the area and shape of the cross section ofthe solder joint at about the middle of its height, which I will referto as the “waist of the joint” or simply the “waist”. Sketch #4 showsthe situation where the distance (gap) between the pads is small and thewaist is still relatively fat. Sketch #5 shows the pads pulled apartmore than in sketch #4 and the waist is slightly smaller than at thebase/pads, as shown in the top view. Sketch #6 shows that the pads havebeen pulled still further more apart, and the waist is still skinnieryet.

[0180] Ref6, Fig. B-4 shows the three cross sections superimposed on topof each other.

[0181] Ref6, Fig. B-5 shows a series of pad pairs, with the distance(gap) between the pads in each pair increasing progressively as thepairs go from left to right. It also shows how the solder joint wouldlook like when the gap between the pads gets higher and higher or largerand larger. The pairs #r4, 5 and 6 were shown in Ref6, Fig. B-3 earlier.Here we can see that the pair #7 and 8 may still be OK, and the waistthere is getting still smaller and smaller or skinnier and skinnier.When we reach a certain large gap, like the one with pair #9, the solderjoint would break and be interrupted. The solder will separate into twoportions. The portion still hanging on to the top pad would look morelike a pillow hanging down from the top pad and may try to look like atear drop except that the shape of the pad, rectangular in this case,and the surface tension of the solder material would influence the shapeof the solder pillow. The portion of solder material remaining on thebottom pad would look like another pillow, whose shape would depend onthe volume of solder available there. See my above discussion aboutthis.

[0182] Ref6, Fig. B-6 shows an enlarged view of pair # 7 & 9.

[0183] Ref6, Fig. B-7 shows a variety of sketches related to what I havediscussed earlier above. Sketch #G is particularly interesting. Itillustrates the fact that the solder joint would adopt the shape of thepad that it is attached to, and then when the solder gets farther awayfrom the pad, then the solder gets away from the influence of the padshape and gets more under the influence of its high surface tension. Thelatter tries to force the solder to become more like a ball or acylinder. This would be the basis for our attempt to manipulate theshape of the joint and its cross section so that we would obtain solderjoints that have ideal cross section shapes so as in turn we wouldoptimize the operating life of our assemblies. For example, by addingthe four protrusions, which I refer to as “Mickey Mouse Ears”, at thecorners of the rectangular pad as shown, we could force the solder jointto have a waist cross section that would be more “rectangular”, i.e.with sharper square corner instead of rounded fillets, in contrast withthe waist shown in Ref6, Fig. B-3 and B-4. We could also refer to thispad shape as the “dog-bone”-shaped pad.

[0184] Now, we will take all the above and go to the next step and applyit to create the proposed solutions as per the invention.

[0185] End of Review Section

BRIEF SUMMARY OF THE INVENTION

[0186] The invention discloses design concepts and means and methodsthat can be used for enhancing the reliability and extending theoperating life of electronic devices, and assemblies incorporating suchdevices, and substrates and/or PCBs, especially if such assemblies areexposed to severe environments such as thermal cycling or power cycling.The main thrust of the invention is to provide flexible joints, such ascolumns, between the attached components, and preferably to orient suchjoints, so that they would present their softest bending directiontowards the thermal center or fixation point of the assemblies. Jointswith rectangular or elongated cross-section are preferred, and theyshould be oriented so that the wide face of each joint would be facingthe thermal center, perpendicular to the thermal deformation rayemanating from the thermal center towards the center of each respectivejoint. The concepts apply equally to leadless packages as well as toleaded packages.

[0187] The same applies to other packages, such as BGAs, where the padsare located on multiple rows or on a matrix, not only along one row nearthe periphery of the package.

[0188] Proposed Designs and Solutions & Their Purpose:

[0189] In Ref5, I have proposed to have the legs of packages to beoriented, such that their wide surfaces would be facing the thermalcenter of the package and/or the assembly. I have described that inRef5, so I don't think I need to repeat the explanations and/or thereasons in this present application again. See particularly FIGS. 4 and5 in Ref5.

[0190] The purpose, summary and gist of the idea in this applicationhere is two-fold:

[0191] It is preferred to use columns as the interconnecting elements,to join chips, packages, etc. to substrates or boards, instead of short,stubby joints. Such short joints usually undergo mostly “shearstresses”. I prefer to have tall joints, which would act like columnsand would undergo mostly “bending stresses”. The reason is that suchcolumns would act as “flex joints” between the two components and wouldabsorb the dimensional differences when such an assembly would beexposed to temperature fluctuations. These flex joints would then beunder bending stresses, compared with the short stubby joints, whichwould be under shear stresses. And by selecting the proper dimensionsfor the columns, we can get the bending stresses down to a level thatwould not reduce the life expectancy of these joints, but would extendit to an acceptable operating life. PS: Since solder relaxes, it is notusually proper to talk about endurance limit, like with steel. Withsolder alloys and the like, the S-N curve keeps dropping down almostindefinitely. But we can specify a maximum bending stress, which wouldgive us a “good/long” or acceptable life expectancy, or in other words,the cross section's short axis would be in line with, or approximatelyin line with, the thermal deformation ray from the thermal center of thedevice to the point under consideration.

[0192] 2. It was also explained that if such columns have a crosssection that is rectangular or elongated in shape, then it would bebeneficial to orient the column and its cross section such that thewider face of the column would be facing toward the thermal center ofthe package or of the assembly.

[0193] Based on the above, I am proposing to create solder joints, to betall, almost like columns, and where the columns would havecross-sections that are more elongated than circular, and that areoriented such that their wider surface of the columns would be facingthe thermal center (TC) of the package or of the (anticipated) assembly,or the short axis of the cross-section in line with the thermaldeformation rays.

[0194] Objectives:

[0195] My goal is three-folds.

[0196] First, I want that the joints between two devices attachedtogether to allow for dimensional changes, without getting overstressedand without failing prematurely. I propose to make such joints as “tall”elements, such as columns, with their column axes generallyperpendicular to the general surfaces of the devices. This applies tosolder joints or any other legs or leads or elements joining two devicesas such.

[0197] Second, I want to make the solder joints, so that the jointswould have a rectangular or elongated cross section, if not round orsquare shape or any other symmetrical shape, and

[0198] Third, I want that the wide side of each joint would be oriented,so as to face the thermal center or fixation point, or in other words,the short axis of the joint cross-section would be approximately in linewith its respective thermal deformation ray.

[0199] Benefits:

[0200] The detrimental effects of Thermal Expansion and Contraction onthe joints, between the components, e.g. the package and the substrate,will be minimized.

[0201] As a side effect of the above, the resistance to shock andvibration will be enhanced, for two reasons. First, the fact that theleads/beams are shaped to have their flat faces oriented to the thermalcenter or the thermal fixation point, makes it that some of the leadswill almost always be present to withstand shock forces coming fromdifferent angle to the package. Second, we can calculate the naturalfrequency of the joints or leads based on their length and geometry, orwe can empirically generate a relation between their length/height andtheir frequency. Then, by knowing what vibration range or vibrationspectrum we want the package to withstand, we can then select the mostappropriate joint or lead dimensions to suit the specific individualcase.

[0202] Some Additional Details

[0203] Some Embodiment Examples of Our Proposed Solution:

[0204] Group One: Attaching the leads/legs to the periphery of thepackage:

[0205] Items 2, 8, 9, 10, 12, 14, 15, 16, 17, and 18 in Table 2 aboveshow examples of such legs, i.e. attached to the periphery of thepackage. I will not elaborate much more here on these legs, because Ithink the idea is already clear enough, and covered enough in Ref3 andRef5.

[0206] Group Two: Attaching the leads/legs to the of the surface of thepackage facing the other component:

[0207] Items 3, 4, 5, 6, 7, 13 and 19 in Table 2 above show legs thatare attached to the surface of the packages, i.e. the surface facing theother component to which the package will be connected. We can call themsurface mounted.

[0208] This kind of “surface mounted” leads/legs/joints will be the maintopic of the first group of products in this application, while “leaded”packages will be in the second group.

[0209] It can be visualized that there could be the following variationsfor such surface mounted leads.

[0210] A. Discrete leads, such as those shown in items 4, 5, 6, 7 and13. These could be preformed and could be soldered at both ends, i.e.one end to be soldered to the package, while the other end to besoldered to the substrate. We could also envision that we could use anappropriate (conductive) adhesive, instead of solder, to attach theleads at either end. The leads would be “oriented” during the attachmentprocess, as shown in item 4, 7, and 13, as per this invention.

[0211] B. Discrete tape-bonded leads. These would be tape/ribbon bonded,as shown in item 20, at one end to one of the components, preferably thepackage. The other end of the lead would be soldered or attached by somemeans, e.g. conductive adhesive, to the substrate. Again, the leadswould be oriented, preferably during the bonding operation, so as toface the thermal center or the thermal fixation point, see definitions,of the assembly, as per this invention.

[0212] C. Discrete Solder Columns: Here again, we can have a number ofvariations and sub-variations. I will describe some of them briefly hereand then will elaborate on a few of them further down below.

[0213] C-1. The discrete solder columns can be formed right on the spot,starting out with a solder ball and then shaping it during the reflowprocess to the desired shape of the flat, with elongated cross-section,oriented column. (See further below).

[0214] C-2. We could also preform the solder column as a generallyflattened, with elongated cross-section, column and hold it in theproper orientation by a carrier wafer or a fixture and then attach it tothe package first, and then to the substrate next. An example would beto take the CCMD solder columns, flatten them under a press or the like,so that each would have an oblong or elongated cross-section, but withthe correct length, then insert each flattened column into a carrierwafer, such that each column would face the central thermal center ofthe package/assembly. (See also Ref5).

[0215] C-3. We could also attach such flattened oriented solder columns,with elongated cross-section, to both the package and substrate in oneoperation, if we use something like the soluble/disappearing carrierwafer. (See also Ref3 & Ref5).

[0216] C4. We could also use an appropriate (conductive) adhesive,instead of the solder, to attach the flattened oriented columns to thepackage and then to the substrate. Again, this can be done in two steps,or in one step, as explained above.

[0217] C-5. We could “grow” the solder columns on the chip (or thepackage), by any of the various methods known in the industry. We justhave to make sure that the cross section of the columns is flattened,with oblong or elongated cross-section, and that the columns areoriented so that the wide surface of the columns faces the thermalcenter, or the short axis of the column cross-section is in line withthe respective thermal deformation ray, as per this invention.

PAGES 61 THROUGH 65 LEFT OUT INTENTIONALLY DETAILED DESCRIPTION OF THEINVENTION—LEADLESS

[0218] Embodiments for Leadless Devices

[0219] Conventional Solder Pads (Prior Art):

[0220]FIG. 1 shows a (Prior Art) conventional LCCC (Leadless CeramicChip Carrier). It shows the solder pads on the periphery. The solderpads are usually rectangular and reach all the way to the outside edgeof the package. The pads are “orthogonal”; i.e. the sides of therectangles are parallel to the package sides and central axes of thepackage. We can see in the figure, the central axes, as well as thecenterlines of the pads at one quadrant of the package. I have labeledthe pads, by “A B C . . . ” for the columns and by “1 2 3 . . . ” forthe rows. We can also see the centerlines of the pads being all onlines, parallel to the package sides and the package centerlines.

[0221] FIG. 2 shows a similar (Prior Art) package, but the solder padsare square, instead of rectangular. We can also visualize that the padscould fill out the whole matrix (or part of it) and the package wouldthen be called a BGA (Ball Grid Array) package.

[0222] FIG. 3 shows another similar (Prior Art) package, but the solderpads here are round (circular), instead of rectangular or square. Again,we can visualize a full matrix (or part of it) of pads, and the packagecould also be considered a BGA.

[0223] Proposed Oriented Solder Pads an Solder Columns

[0224] FIG. 4 shows a package similar to the one shown in FIG. 3, i.e.with round solder pads. I am showing only the top right quadrant, butthe same will apply to all the other three quadrants as well. They willbe mirror images of the first quadrant shown. I have drawn new “rays”propagating from the geometric center of the package and going to thecenter point of each and every solder pad. We can easily consider herethe geometric center of the package to be the “thermal center” of thepackage as well, as explained in the above definitions. These raysrepresent the direction of any expansion or contraction that may occurin the component or assembly, if they were exposed to thermal cycling orpower cycling.

[0225] If we have a point of the package, “fixed” in space, then thatpoint will act as the anchor, and all the thermal deformations willstart or originate from that point. Hence, we can say that this“fixation point” is acting also as the new/effective “thermal fixationpoint”, which would be equivalent to the “thermal center”. In such acase, all the thermal deformation rays will then be emanating from this“fixation point”. Again, this is in accordance with the earlierdefinitions.

[0226] According to this present invention, all the leads/legs/jointswill have to be facing this thermal center or the thermal fixationpoint.

[0227] I have added another line inside each of the solder pads. This isa line that is perpendicular to each thermal deformation ray, whichstarts at the thermal center or the thermal fixation center of thepackage and proceeds to each individual pad. This new line would give usthe preferred direction of bending axis of each respective solder column(or leg or lead), if we want to minimize the (bending) stresses on thatcolumn during the thermal expansion and contraction of the assembly. Wewill refer to this line as the “preferred bending line”, or simply the“bending line” “for its respective pad”. [DEFINITION]. We can notice andappreciate that the direction of the bending line inside each solder padis different than that of the adjacent ones, because the direction ofthe thermal deformation rays changes continuously as we go from one padto the next, to the next, etc.

[0228] Inside each solder pad, there are two additional lines. They areparallel to the bending line, one on either side of it and at a certaindistance from it. These two lines will define the shape of the newrectangular solder pads, according to this invention.

[0229]FIG. 5 shows the new proposed solder pads. They have a generallyrectangular shape. Their width and length can be selected to suit theindividual case and package. For this example, I have selected therectangles to be 0.001×0.025 inch. The distance between the centerpoints of each pad and the adjacent one (pitch) in this case is 0.050inch. Please notice that each rectangular solder pad has its long sidesparallel to the bending line at that specific pad at that specificlocation, which in turn is perpendicular to the thermal deformation rayfor that point. Hence as stated earlier, the direction angle of eachsolder pad would progressively increase as the pads go around theperimeter of the package. This is the shape and orientation of theproposed oriented solder pads, as per present invention.

[0230] FIG. 6 shows a 3-D view of the package shown in FIG. 5, showingthe oriented rectangular pads of the package.

[0231] Now, if we build our solder columns on top of each of these pads,such that the columns would generally have a cross section generallysimilar to these solder pads, and would be oriented in the samerespective direction of each individual pad, then the new solder columnswould have minimum bending stresses applied on them during any relativemotion between the package and the substrate, for example during athermal cycling situation.

[0232] FIGS. 7, 8 and 9 show also 3-D views of the columns on top of thepads, which were shown in FIGS. 5 and 6. Note that these are all alongthe edges of the package, and are usually called “peripheral” pads.FIGS. 8 and 9 are zooming in on different parts of the package. FIG. 8shows the top corner and FIG. 9 shows the left-hand side corner.

[0233] FIG. 10 shows a 3-D view of a BGA, where the solder pads havebeen made as per this invention, i.e. oriented and facing the thermalcenter of the package. I am showing seven concentric rows of pads, butthere could be as many as required or as many as specified by the“standards”.

[0234] All the pads are located along their standard conventionalorthogonal lines, i.e. the “center point” of each pad is on a line,which is parallel to the sides or the center lines of the package, andat the proper pitch, etc. These locations are exactly as specified byJEDEC or by any other standards, for standard conventional BGAs. Theonly difference is the shape of the pads and their orientations.

[0235] However, the pads themselves are not as specified for standardconventional pads. They are according to this present invention, i.e.they are rectangular in shape, and they are oriented, such that their“bending line” is perpendicular to the thermal deformation ray, whichstarts at the thermal center of the package and goes through the centerpoint of each respective/individual pad.

[0236] FIG. 11 shows a similar BGA as the one shown in FIG. 10, exceptthat it also shows the columns on each individual pad.

[0237] FIGS. 12 and 13 show enlarged views of FIG. 11.

[0238] Methods for Providing the Desired Tall Rectangular Columns

[0239] There is a number of ways or methods for making these orientedgenerally rectangular solder columns. Some are well know to the industryand some are new and novel as per this invention.

[0240] There are several ways to manufacture the above embodiments. Inmany cases, several methods can be applicable to the differentembodiments. I will show these methods here below.

[0241] Applying the Solder Balls:

[0242] FIG. 14 through 16 show a chip or LCCC like the ones shown inFIGS. 5 and 6, but with a solder ball applied to each one of thecontact/solder pads. The figures show the drawings in progressivelysmall and large scale, i.e. as if we are zooming in on the package. FIG.14 shows the first quadrant, i.e. top, right quadrant of the package.FIG. 15 is zooming in on the top corner of the package, and FIG. 16 onthe left corner. You can see that there are rectangular pads under eachone of these solder balls.

[0243] In FIG. 17, we see that we have two components (LCCC's) that wewant to join together. The lower one has already the solder ballsattached to the oriented rectangular pads. The top LCCC has the solderpads also rectangular in shape and oriented as proposed by thisinvention, in other words, they match their respective counterparts onthe lower device, both in shape and in orientation. The arrow in thefigure indicates that we will move the top package on top of the bottomone.

[0244] FIG. 18 shows the top package lying on top of the bottom one. Thetop package is shown as if it “transparent”, simply to be able to seethrough and see what is lying underneath.

[0245] We see along one side of the package, a set of dimension lines,marked “A”, “B”, and “C”. These indicate the distance or height or gapbetween the two devices. The dimension or gap “A” indicates the gap whenthe top package is sitting on top of the solder balls. When the solderballs are molten, then we would, by some means that will be explainedlater, pull the top package a little bit away from the bottom package,to increase the gap between them to the gap marked “B”. This wouldchange the shape of the solder joint from spherical to rectangular. Thiswill reduce the stresses on the solder joints. If we want to reduce thestresses on the joints even more, we would then pull the packagesfurther apart to make the gap equal to “C” or close to it. Although thiswould make the total assembly slightly larger/higher/thicker, it wouldreduce the stresses in the solder joints and improve the life expectancyof the assembly. When we go from gap “B” to gap “C”, the solder columnswill change in shape from a uniform rectangular column to a “starved”column shape, as we talked about earlier, in the BACKGROUND Section, andas will be shown in the following figures.

[0246] FIGS. 19 and 20 show one side of the top package, as if it is cutoff along the edges of its rectangular pads. This is done, so as to beable to see how the top and bottom pads line up together and how thesolder balls lie in between. FIG. 19 still shows the body of the packagein place but show it as if it is transparent. FIG. 20 shows that thispart of the body has been removed all the way to the “cut” line. You cansee, most clearly in this FIG. 20, that the bottom edge of the cut inthe top package is above the bottom package by the distance “A”.

[0247] FIG. 21 shows the solder columns when they have been formed totook like “uniform” rectangular columns. Again, it shows the columnssitting on top of the bottom package as if the top package has beenremoved, but with the top pads of the top package still being shown inplace. The figure shows the cut edge removed. Notice that the gapbetween the two packages has increased from “A” to “B”.

[0248] FIG. 22 shows the same assembly after the gap between the twopackages has been increased from “B” to “C”. The columns have beenstretched beyond the “uniform rectangular columns” condition shown inFIG. 21 above, to a point where the column “waist” has thinned down, asshown. I refer to this condition of columns as “STARVED” COLUMNS”.

[0249] FIG. 23 through 25 show the same thing, but after removing thetop package, just for clarity. They show the starved columns standing ona BGA. They are obviously oriented, as per the present invention. FIG.24 zooms in on the top corner of the package, while FIG. 25 zooms in onthe left corner.

[0250] Such starved columns can be produced this way, i.e. directly on aBGA or a chip or any such device, by a progressive process of repeatedmasking and deposition or screen printing, as will be explained later.

[0251] FIGS. 26 and 27 show the progression or rather the evolution ofthe solder joint.

[0252] All the figures in FIG. 26 are shown in the “wire form” format.In other words, the hidden lines have not been removed. FIG. 27 showsthe same figures shown in FIG. 26, but with the hidden lines removed.

[0253] FIG. 26-A shows the conventional (truncated) solder ball on topof a conventional round pad.

[0254] FIG. 26-B shows the same ball, but on top of a rectangular pad,which ideally would also be oriented properly, as per present invention.

[0255] FIG. 26-C shows a uniform rectangular column, superimposed on topof the figure shown in FIG. 26-B. The column is supposed to have thesame “volume” as the ball. I did calculate the dimension of the column,such that both bodies do have the same volume. See calculations below.It is also assumed that the solder column has exactly straight verticalsides, i.e. that the solder is not bulging out creating a “fat” solderjoint, nor is it sucking in creating a “skinny” solder joint. See Figs.B-1 through B-7. Ref6, pages OC-D-05 through OC-11.

[0256] FIG. 26-D shows the uniform rectangular column by itself.

[0257] FIG. 26-E shows the starved column, superimposed on top of theuniform rectangular column. Again, they both have the same volume.

[0258] FIG. 26-F shows the three bodies superimposed one on top of eachother, just to emphasize the point, that they all have the same volume,although their shapes are so much different from each other.

[0259] FIG. 28 is the same as FIG. 26-F, except that it shows somenomenclature. This is to support in visualizng some of the terms givenin the “DEFINITIONS” section earlier.

[0260] Some Alternative Methods to Stretch the Columns,

[0261] 1—Use Cored Solder Balls, or Conventional Solder Balls withStand-Offs

[0262] FIG. 29 gives an illustrative summary of the proposed process.

[0263] In essence, we start with solder balls that have a core ofspecial material, which is coated with a relatively thin layer ofsolder. The core can be made of a solder alloy that has a higher meltingtemperature, or can be made of copper or even a glass sphere, or thelike. We'll refer to such solder balls as “cored” solder balls.

[0264] We place such cored solder balls on the pads of the package or ofthe substrate, as in FIG. 29-A. The size of the core and the amount ofmeltable solder on top of the core, have to be calculated, so as toaccomplish the desired end results, as explained below. The size of thecore will be such that it will provide the proper height of theresulting end solder joint, and the size of the ball will be chosen,such that the amount of solder will not be enough to create a fat solderjoint. It would rather give us the desired starved joint.

[0265] The end result is that when we place the mating package on top ofanother package or substrate, as in FIG. 29-A, and reflow, then thesolder would melt and will start to wet both the top and bottom pads.The non-meltable core would either float in the middle of the joint, orfall to the bottom, or even may rise to the top, depending on itsspecific gravity and that of the molten solder.

[0266] The solder will wet the pads. But the amount of solder would havebeen chosen, such that there will not be enough solder to create a fatsolder joint, even with the presence of the core. It will wet the twopads and spread as much as possible over the whole surface of each pad,but eventually, the top package would drop and fall towards the bottompackage, and finally would come to rest on top of the cores, as in FIG.29-B. The cores will act as “stops” or “stand-offs”, and will controlthe spacing or gap between the two devices.

[0267] The end effect will be that we will have solder joints that havelarge pads, or “feet”, but with a narrower waist.

[0268] This will work with rectangular pads, as well as with round orsquare pads, too.

[0269] FIG. 29-C shows a similar arrangement, but with an externalstand-off, separate from the solder cores. In this case, the externalstand-offs, will control the spacing, instead of the cores, assumingthat the external stand-offs are larger/taller than the cores. Also, inthis case, we could just as well start with conventional solder balls,i.e. without any special core as described above, and rely on thestand-offs to control the height of the end resulting columns.

[0270] In either case, the stand-offs will have to have a total heightthat is slightly smaller than the diameter of the balls, or the totalheight of the balls in case the balls are truncated. The reason is thatthe balls need to touch the pads and wet them before the stand-offs takeover.

[0271] 3—Use Controlled Volume Preform and Individual/SeparateStand-Offs

[0272] FIG. 30 illustrates this method.

[0273] FIGS. 30-A and 30-B show an overview of the idea. We start with apreform, as shown, which has the proper predetermined volume “VP”, whichwould be needed for the final end result, which is to obtain the StarvedColumns that we want to end up with. The preform is taller than thefinal starved column, but it is skinnier. The preform can be a uniformcylinder, as shown in FIG. 30-A, or it can have a conical shape, as inFIG. 30-B.

[0274] Note: The conical shape preform in FIG. 30-B looks like a priorart design covered by a patent issued to IBM or AT&T ??, but I don'tremember the patent number. I think it was called “solder cones”. Thecones were cast on the package.

[0275] Some “stand-offs” or “stops” would be placed between the twodevices, to control the distance between them during the reflow process.The height of the stand-off would be smaller (shorter) than the heightof the preforms.

[0276] a) Reflow without Stand-Offs. (See Top Figures of FIG. 30)

[0277] Let's first see what would happen, if we reflow the solderpreform, without having the stand-offs.

[0278] Let's say we have the preform attached to the top device pads,and let's say that it is a BGA package. Sometimes, such a package withcolumns sticking out from its bottom is referred to as a “dead roach” orsimply a “roach”. It will also look very much like a Pin Grid ArrayPackage (PGAP), except that the legs will be made out of those solderpreforms.

[0279] Let's also say that the bottom device is another package or asubstrate or rather, a PCB.

[0280] We place the roached BGA on the PCB, as in FIG. 30-A or -B. I amshowing only one preform and one stand-off here, just for clarity.

[0281] At this point in time, i.e. before the reflow process, thedistance between the BGA and the PCB pads will be practically equal tothe height of the preforms, plus whatever non-planarity that may beatthe tips of the preforms. The pads themselves have their own thickness,which will add to the total gap between the bodies of the BGA and thePCB.

[0282] When we start the reflow process, the solder preforms will softenand start to melt. The bottom tips of the tallest preforms would besitting on top of the PCB pads. If some preforms are slightly shorter,due to manufacturing tolerances, they will not be touching theirrespective PCB pads. In order to enhance the wetting, we can apply someflux on the PCB pads, or even some solder paste. This would help inconnecting the preform to the pads and to transfer heat, and in keepingthe surfaces of the pads clean, etc.

[0283] Once the taller preforms start to melt and the top BGA starts tomove downwards, due to its own weight or due to some external forces,then these shorter preforms will reach their respective PCB pads andtouch and wet.

[0284] I figured that one good way to explain the concept is to use someconcrete dimensions, as in the example shown in FIG. 30. I will usethese abbreviations for the various dimensions, which I have selectedfor this example:

[0285] DC is the diameter of a Circular pad, which we will assume to be0.025 inch. See FIG. 30-C.

[0286] AC is the Area of the Circular pad. The area AC will be equal to(π/4×DC{circumflex over ( )}2)=4.91E-04 inch square.

[0287] LR is the Length of a Rectangular pad, which we will assume tohave a length of 0.025 inch. See FIG. 30-D.

[0288] WR is the Width of the Rectangular pad, which we will assume tohave a length of 0.010 inch.

[0289] AR is the Area of the Rectangular pad, which we will assume tohave a length of LR and a width of WR. AR will be equal to(LR×WR)=2.50E-04 inch square.

[0290] DP is the diameter of the Preform, which we will assume to be0.010 inch. See FIG. 30A & C.

[0291] AP is the cross-section Area of the Preform. The area AP will beequal to (π/4×DP{circumflex over ( )}2)=7.85E-05 inch square.

[0292] HS is the Height of the “Starved” solder joint, which we willobtain on top of the Rectangular pads, as per this invention. Therectangular pad in this case will be similar to the above one, i.e. witha length LR and a width WR. For this example, I have decided to makethis Height=0.025 inch. See FIG. 30-G.

[0293] VS is the volume of the Starved solder joint. This volume can becalculated in different ways. I have sliced it into several thintrapezoidal shapes, calculated the volume of each and added themtogether to get an approximate volume of the total starved column. Forthe starved column that I am using here, the volume VS is xxx, for acolumn height HS of 0.025 inch, on a Rectangular pad of length LS of0.025 inch and a width WS of 0.010 inch. This is assuming a certaincurvature for the sides of the column, which is as shown in all myfigures.

[0294] With all these assumptions, the volume VS turns out to be=2.96E-06 inch cube.

[0295] We will calculate the following dimensions now here below.

[0296] VP is the volume of the Preform and it is equal to (AP×HP).

[0297] VC is the volume of the Circular solder joint and it is equal to(AC×HC).

[0298] VR is the volume of the Rectangular solder joint and it is equalto (AR×HR).

[0299] HC is the Height of the “uniform” solder joint, which we willobtain on top of the Circular pads.

[0300] HR is the Height of the “uniform” solder joint, which we willobtain on top of the Rectangular pads.

[0301] HP is the Height of the Preform.

[0302] Since we can easily assume that the volume of solder, not solderpaste, will not change, and since we have decided and determined thatthe volume of the end resulting Starved columns VS is =2.96E-06 inchcube, then all the other volumes, i.e. VP, VC and VR, will also equalthat same volume. We will use this knowledge/assumption/fact todetermine the three remaining unknown values, i.e. HC, HR and HP. Forthese calculations here, we will assume that there are no solder filletsto affect our calculations.

[0303] We will now proceed with the case, where there are no stand-offsin this case.

[0304] In FIG. 30-C, we will also assume that the pads are Circular, andhave a diameter DC of 0.025 inch, hence a surface area of 4.91E-04 inchsquare.

[0305] When the preforms will melt, each preform will try to wet all thesurface of its respective pads and still tries to stay as one single“lump” of solder. The top BGA will drop and will create solder joints,connecting each BGA pad to its corresponding PCB pad. These solderjoints would have a similar shape as the pads, but they would have amuch shorter height (HC), than the preform's original height (BP).

[0306] It is easy to calculate the joint height HC in this case, usingsimple mathematics.

[0307] The volume of the solder in the solder joint VC is =2.96E-06 inchcube, as discussed above. The area of its circular pad AC is =4.91E-04inch square. Hence, the height HC of this solder joint is =VC/AC=0.0060inch.

[0308] Note that we are assuming that the circular solder joint willhave straight vertical wall, i.e. the joint is not fat or skinny, andthat there will be no fillets effect.

[0309] This means that, for the same amount of solder that we need tocreate the 0.025 inch tall Starved column on a Rectangular pad that is0.025 long by 0.010 wide, we would get a solder joint height of only0.006 inch, if we had used a circular pad of 0.025 inch diameter.

[0310] In FIG. 30-D, we will again assume that the pads are Rectangular,and have a length LR of 0.025 inch and a width WR of 0.010 inch.

[0311] When the preforms will melt, again each preform will try to wetall the surface of its respective pads and still tries to stay as onesingle “lump” of solder. The top BGA will drop and will create solderjoints, connecting each BGA pad to its corresponding PCB pad. Thesesolder joints would have a similar shape as the pads, but their heightHR will be different.

[0312] Again, it is easy to calculate the joint height HR in this case,using similar mathematics, as above.

[0313] The volume of the solder joint VR is still =2.96E-06 inch cube,as discussed above. The area of its Rectangular pad AR is =2.50E-04 inchsquare. Hence, the height HR of this solder joint is =VR/AR=0.0118 inch.

[0314] Note that we are again assuming that the Rectangular solder jointwill have straight vertical wall, i.e. the joint is not fat or skinny,and again there is no fillets effect.

[0315] b) Reflow with Stand-Offs. (See Bottom Figures in FIG. 30)

[0316] Now, we will compare the above case with a case where we do use“stand-offs” or “stops”.

[0317] We will arrange to have the height of the stand-offs to be equalto the height of the Starved columns, plus the thickness of the solderpads on the BGA and the PCB. This is because the stand-off will not beplaced between the pads themselves, but between the body of the BGA andthe general surface of the PCB. If we assume that both groups of padsare 0.005 inch thick, then the height of the stand-offs should beHS+0.005+0.005=0.035 inch.

[0318] We have also decided to make the Preform with a diameter DP of0.010 inch, hence its cross-section area AP is =7.85E-05 inch square.

[0319] And since we know that the volume VP of the Preform is equal tothe volume VS of the Starved column, which is =2.96E-06 inch cube, wecan now calculate the height HP of the Preform. HP will be =VP/AP=0.377inch.

[0320] This is the height of the Preform between the pads.

[0321] This means that the distance between the body of the BGA and thegeneral body of the PCB would be=0.0377+0.005+0.005=0.0477 inch. Thisgives us the height of the Stand-Off, which then should be =0.0477 inch.

[0322] According to all the above calculations, we can see that, duringthe reflow process, the Preforms will collapse through a distance=0.0377-0.0250=0.0127 inch.

[0323] Other Preform Shapes

[0324] A similar situation would occur if the preforms were made ofdifferent shapes, but still with the same volume. For example, thepreforms can have a conical shape as in FIG. 30-B or E. As long as thevolume is still equal to VP, i.e. the volume of the cylindrical preformdescribed above, and all other parameters stay the same, then we shouldend up with the same height for the solder joints. Conical preforms canbe cast directly on the BGA, more easily than if we would want to attachcylindrical preforms to the same package.

[0325] 3 Use Solder Paste and Stand-Offs

[0326] A variation to the above method is to start with solder paste,that we would apply to one device, or to both. Ideally, the paste wouldbe shaped as a “cone”, so that the volume/amount of solder would belimited. We would have “stops” or “stand-offs”, as in FIG. 28C. Thisleads us in a way into the next alternative. See Alternative 3, for thereason of having cones, i.e. tall shapes but with limited volume.

[0327] Special Embodiments

[0328] The above examples, using the preforms and the standoffs oncircular pads, or even on square pads, i.e. on standard conventionalpackages and pads, can also be used in the industry, simply to providethe assemblies with “flexjoints”, and thus enhance their reliability andextend their operating life, compared with the normal cases of havingshort stubby solder joints.

[0329] We could extend this same thinking and apply it to other shapesof pads. For example the pads could be rectangular, or elliptical oroblong or elongated in any desirable fashion.

[0330] Then, the pads could also be “oriented” as per the presentinvention, to take advantage of the additional expected benefits.

[0331] 4—Shape Memory Method

[0332] We can also use shape memory materials, e.g. shape memory plasticlike the one used by Raychem Corporation, now TYCO, to make their heatshrink tubing. We could also use shape memory metals, again used byRaychem. These metals include Tinel, which is a trade name for an alloyof Titanium Nickel, or Betalloy, which is a trade name for a shapememory Copper Alloy. Betalloy is also used to make eyeglasses frames,which can be deformed at will and when they get placed under a hot waterfaucet and the hot water hits them, they jump back to their originalshape.

[0333] We can use such shape memory materials, plastics or metals, tocreate the “lifting” devices/means, to increase the distance between themating pads and to stretch the solder joints/columns.

[0334] So, FIGS. 31 through 33 give examples of such a lifting device.They show a frame of some sort, which would have the desired “lifting”features. These could have a sort of a “lip” that would lodge betweenthe package and the substrate. The lip would have been made originallywith a certain thickness/height. Then it would be cross-linked to keepits original manufactured shape in memory. Then it would be compressedcold, to make it thinner at room temperature. Then it would be placebetween the substrate and the package. When the stack gets in the ovento reflow the solder, the solder would melt and attach to both thesubstrate and the package, and then at the right time and/ortemperature, the lip would activate and remember its original shape andthickness, so it would lift the package increasing the gap between thepackage and the substrate, thus stretching the solder columns to theirdesired shape.

[0335] 5—Selective Heating Method

[0336] We could also activate the memory of the lifting elements byother means. For example, using selective frequency lasers. We could usea laser with the proper frequency to melt and reflow the solder whilethe lifting elements are still dormant. When we know that the solder hasmolten and is attached to both the package and the substrate, then weactivate the laser with a different frequency which would then wake upthe memory of the lift elements so that they would lift the package andincrease the gap and thus stretch the columns to the desired height andshape.

[0337] The frame with the lift elements can be made to be removed afterthe soldering operation is completed. It could be made with somebreakaway tabs to facilitate its removal. It could also be made out amaterial that could be dissolved and removed this way, e.g. like thecarrying wafer that was used with the CCMD. See Ref14, U.S. Pat. No.4,655,382, invented by Geoffrey B. Wong, et al., and who were members ofthe effort on that project. In this case, we could have the liftingelements inserted in a similar dissolvable carrying wafer.

[0338] The lift elements could be made out of Betalloy or Tinel asmentioned above, and could be incorporated in the frame or in any othercontraption that is suitable.

[0339] The lifting could be done also by other means, such as fixturingof any suitable shape or form, as desired by the particular user ormanufacturer.

[0340] 6—Lifting Element with Large TCE

[0341] Instead of using devices made of shape memory material to liftthe top package, say the BGA, and to increase the gap between it and thelower PCB, we can use a lifting elements made out of a material that hasa relatively large TCE. We could for example use a foam material,possibly closed cell foam, which would expand at a considerably largerrate than the other components in the assembly. We would place such alifting means, let's just call it the foam, between the BGA and the PCB,where the foam would be much thinner than the height “H2”. During thereflow, the foam would expand but would still be smaller than the height“H2”, up to a certain point or rather up to a certain temperature. Whenthe temperature reaches the liquidus temperature of the solder and thesolder would melt totally, then the thickness of the foam will be justabout equal to the height “H2”, just a little thinner. So, up to thistemperature, the foam has not done any lifting. Then when the tempexceed the melting temp of the solder, and is in the reflow holdingzone, the foam will expand to a larger size and will lift the BGA andincrease the gap to H2 and then to goes beyond to H3, as required.

Other Embodiments of Oriented and Starved Solder Columns

[0342] A. Tall Preforms “Fall” on the Stops and Package Rests on the“Stops” (Devices and Methods):

[0343] Fill the solder with copper particle, so that we can shape itinto the required preform shapes, like the “LONG CONES”, or the “½TAPERED AND REST CYLINDRICAL COMPOSITE CONES”, etc.

[0344] Preforms will be TALL AND SLENDER, Taller than the end-height ofthe finished column. The volume of the preform will be the same as thevolume of the finished column. But since the finished column will belarge at the base of the BGA and of the PCB, and May West at the center,then for the same volume, the height will be shorter.

[0345] During reflow of the tall slender preforms, the BGA will “fall”or “drop” down, until its stops at the correct height, sitting on the“stops”, which will control the ultimate height of the solder columns.

[0346] B. Regular Solder Balls “Lifted” by “Magic” (Devices andMethods):

[0347] The solder balls are of regular, spherical shapes, or truncatedspherical shapes.

[0348] The BGA is placed on the PCB and the solder is reflowed thenormal way.

[0349] The BGA is lifted while the solder is molten, so that the solderjoint gets stretched.

[0350] The molten solder will stay sticking to the solder pads on thePCB as well as on the BGA and will have a cross section that will matchpretty closely the shape of the respective contact pads at each end ofthe solder joint.

[0351] The center portion, between the two pads, will get thinner andwill form an hour glass shape, or a “May West” waist shape.

[0352] By controlling the volume of the original solder ball and theareas of the contact pads of the PCB and of the BGA, and also theultimate height of the “stretched” solder column, we can calculatepretty close enough, the new height of the solder joint. We will callthis “stretched or starved” solder column.

[0353] C. The “Magic” that will “Lift” the BGA

[0354] We can have an element placed between the BGA and the PCB, whichwould expand in its height so that the BGA gets lifter, AFTER THE SOLDERHAS MOLTEN AND HAS ATTACHED ITSELF TO THE CONTACT PADS OF BOTH THE BGAAND THE PCB.

[0355] The element can be made of expandable plastic, either using SHAPEMEMORY Features or using a foam plastic with certain “air” or othermaterial.

[0356] The solder used for these assemblies could also be “filledsolder”, e.g. solder mixed with particles of copper or the like, to makeit stick together and hold its shape better and longer than regular(unfilled) solder. Such filled solder is already in the prior art, and Ihave known it and encountered it since 1980 when I was working on myCCMD. However, I could not find it, when I did a patent search recently.

[0357] We could also use “conductive adhesives” to create and/or toattach these oriented rectangular columns or starved columns, with orwithout solder, or with or without filled solder.

[0358] We could also start with the same preform material (column wirestock) that I had used for the CCMD, flatten it and insert it intocarrier wafer, which have “oriented” holes and where the flattenedcolumns will be properly oriented, and then use that to mount packageson substrates.

[0359] FIG. 34 shows some other embodiments that could be used toaccomplish the same end goals. For example, a) We could use twowire-bonded wires, side by side to simulate the effect of therectangular columns. B) We could use the wires and mount them in placeusing conductive adhesive, if we do not want to use the wire bondingtechnique.

[0360] The left bottom figure/sketch in FIG. 35 shows one way to “grow”a uniform rectangular solder column, using for example the masking anddeposition techniques used for the manufacturing of chips or multilayerboards, or simply using solder masks and the like.

[0361] We can also envision, that by using multiple, repeated steps ofmasking and deposition, we can shape the solder columns to have, alreadyfrom the start, the desired end-shape of the hour-glass or the Mae Westform, or a shape approximately close enough to it. This can easily beaccomplished, say, by starting a first masking and deposition step,where the lower one third of the column would be large, then we wouldrepeat the masking and deposition step, but with a narrowercross-section for the solder column, and then finally the third maskingand deposition step would have again a large cross-section for thesolder column. This would produce a solder column that has three sizesof cross-sections, step-wise, or step-shape profile. During the reflow,the shape will change from a step-shape profile, to a rathersmooth-curve profile, due to the high surface tension of the solder.More than three steps could be used if necessary.

[0362] The right bottom figure shows a cross section of the figure onthe left, but shows also the package sitting on top of the “grown soldercolumn” and also we could add some solder cream that could screenprinted, so as to facilitate the wetting of the solder column to thepads on the substrate and/or package.

[0363] Oriented Sockets & Universal Sockets

[0364] Once these packages and substrates with oriented pads becomepopular and used on the market, then we will need sockets that canhandle such packages and can sit and be mounted on such substrates. Itis easy to make such sockets and connectors. Simply install the contactsprings in a way that would match the orientation of the pads, “etvoila!”. Such sockets and connectors are part of this invention as welland I would like to claim them as well.

[0365] Other Quick Thoughts:

[0366] Based on the above, I am proposing to create solder columns thathave a cross-section that is more elongated than circular, and where thecolumns are oriented such that their wider surface would be facing thethermal center of the package or of the anticipated assembly.

[0367] Another basis for this invention is the fact that a solder jointin general usually follow the shape of the solder pads it is attachedto.

[0368] For that reason, I propose to shape the solder pads so as to beconducive to creating such solder joints.

[0369] So, the solder pads should be shaped to fit/suit the desiredultimate shape of the column.

[0370] For example, if the column is desired to have a roughlyrectangular cross-section, then the solder pad should also have roughlya rectangular shape.

[0371] The effect of the shape of the solder pad on the shape of thecolumn cross-section does fade away as we move away farther from the padalong the solder column length/height.

[0372] For example, if we start with square solder pads on both thepackage and the substrate, which will be joined together by a solderjoint, then the following would be expected.

[0373] If the space between the two pads is very narrow (short height,or short gap or space between the pads), then the solder joint will havepractically the same shape as the two solder pads, i.e. square, assumingthe proper volume of solder is used.

[0374] If the solder volume is too large for the space available, the nthe solder would bulge out and may even overflow. If allowed to float,then the joint may become higher/taller as well.

[0375] If the volume is too small, and if the height/space is allowed tofloat, then the thickness/height of the joint would be smaller.

[0376] If the proper volume is provided, and if the two pads were pulledapart a certain distance, then we would be forming a “column”. The shapeof the column would depend on the ratio of H/S, where H is the Heightand S is the Side of the square.

[0377] For a small H/S, the cross-section of the column would berelatively uniform as a square throughout its whole height or length ofthe column.

[0378] If H/S get larger, then the column cross-section, near the pads,would still be square, and then the further away we go, away from thepads towards the mid-height of the column, the cross-section of thecolumn will start to get more rounded at the corners, or ratherfilleted, until at a certain point or height, it may reach a circularshape, rather than a square.

[0379] Another similar example is when we start with rectangular pads.

[0380] The same thing would happen, but starting with a rectangularbasis.

[0381] If the solder joint is short, then the joint is exactlyrectangular.

[0382] If we increase the height to a relatively small/medium height,then the joint will be exactly rectangular at base (pads), and thefarther we get away from the pads the more rounded (filleted) thecorners of the rectangle, and when the column gets pretty tall, then atthe center of the column, close to its mid-height, i.e. at mid-distancebetween the pads, we would get an ellipse, and for even taller columnsyet, we may even get a circular cross-section at the mid-height of thecolumn.

[0383] Separation and the Use of Supported or Filled Solder

[0384] All the above is assuming that the solder would not separate andcut-off into two separate individual portions, where one portion wouldstick/adhere to the lower pad and the other portion would stick/adhereto the upper pad, or it may even separate totally from the top pad andthe whole amount of solder would sit on top of the lower pad.

[0385] I had solved this problem as seen in two of my previousinventions. Please see Ref15. U.S. Pat. No. 4,664,309, dated May 12,1987, entitled “CHIP MOUNTING DEVICE”; and Ref16. U.S. Pat. No.4,705,205, dated Nov. 10, 1987, entitled “CHIP CARRIER MOUNTING DEVICE”.There, I have “supported” the solder, by wrapping a thin narrow band(ribbon) of copper tape around the solder column, to keep its columnarshape.

[0386] If we find it necessary in certain cases here, then we can use asimilar approach for this present invention.

[0387] There is a difference, however. In the CCMD case, the height ofthe columns were staying practically constant. In this presentinvention, the columns change their height as described herein.

[0388] We can absorb the difference, i.e. the change in height of thecolumns, by using a thin wire to wrap around the solder column, in sucha way that the wire would be more flexible than the ribbon tape. Thethin wire, preferably with a round cross-section, instead of therectangular cross-section of the ribbon, would be more flexible and morereceptive to allowing the column to compress or to stretch.

[0389] Another change that we can introduce, over the CCMD, is toflatten the CCMD columns. The CCMD columns were made in a continuousshape, like a continuous wire. We called it the “columns wire stock” orsimply the “wire stock”. The wire stock was then cut to the properlength, to create the “preforms”, and then the preforms were insertedinto fixtures, sometimes we used dissolvable carrying wafer, to be usedfor the assembly process.

[0390] We can do the same thing here, except for two additional steps.

[0391] First, we need to “flatten” the wire stock. After the wire stockis formed, using the thin wire instead of the ribbon, we can run thewire stock between two rolls under pressure, to “flatten” the wirestock.

[0392] Second, when the wire stock is cut to the proper length of theindividual preforms, each preform would be oriented, as per the presentinvention, when it is inserted into the carrying fixture or the carryingwafer, or when it is attached to the packages, regardless of the methodof attachment.

[0393] Another alternative is to use “filed” solder.

[0394] The term filled solder had been used in an old patent, that Iencountered around 1980-84, when I was working on the CCMD. That patenthas included some copper particles into the solder, homogeneouslydispersed in the solder. I had wanted to use that approach myself as analternate method of maintaining the shape of the solder columns, butbecause of that prior art. I was told that I could not claim myselfanymore. That prior art patent wanted to use that filled solder to closelarge gaps between copper plates or the like. Because of the copperfiller, the solder was supposed to maintain the shape given to it,overcoming the high surface tension of the solder.

[0395] I did a patent search on filled solder, but I could not find thatold prior art patent.

[0396] Regardless, that patent is now in the public domain, since it hasbeen over 17/20 years since the time I encountered it.

[0397] So, if we make oriented starved columns as per present invention,and encounter cases, where the regular solder does separate, then we canuse “filled solder” as described above, to reduce or eliminate theseparations. Filled solder would allow us to have taller starvedcolumns, without separation, than if we were to use regular, i.e.unfilled, solder. Hence, taller columns without separation.

[0398] Double Wires

[0399] FIG. 34 shows another method to create solder columns as perpresent invention. It is a way to simulate the flat columns, and toorient them as desired. We would have two round wires, placed near eachother, both on each of the solder pads, to simulate the effect of acolumn with rectangular cross-section. The plane, which contains thevertical axes of the two wires, would need to be oriented, so as to facethe thermal center. The two wires could be “wire-bonded” to one device,e.g. the BGA, and then soldered to the other device, e.g. the PCB.

[0400] Solder Bumping

[0401] FIG. 35 shows a method of “bumping” the solder pads, so that theywould have tall solder columns. FIG. 34-A shows one such method ofbumping. This can be done by “deposition” on top of the chip, or byscreen printing the proper solder paste on the substrates or on theBGAs.

[0402] All these methods are well know in the industry and are notnovel.

[0403] The novelty here is two-fold.

[0404] First, that the solder bump would have a rectangular or elongatedcross-section, as implied by the rectangular opening in the mask shownin FIG. 34-B. FIG. 34-B shows a mask that could be used to create such asolder column/bump, with a rectangular or elongated cross-section, wherethe opening or aperture in the mask is rectangular or elongated asneeded.

[0405] Second, the fact that these solder bumps would be “oriented” asper the present invention. This means that the flat face of each solderbump, or column for that matter, would be facing the thermal center ofthe package or of the assembly, or in other words, the short axis of thesolder bump cross-section would be in the direction of the thermaldeformation ray to that specific bump. Hence, each opening or aperturein the mask should be oriented, as needed, to satisfy the requirements,as per present invention.

PAGES 100 THROUGH 110 LEFT OUT INTENTIONALLY SPECIFIC BACKGROUND—LEADEDFIELD OF THE INVENTION

[0406] This section of the specification relates to and covers thesecond group of products, which includes LEADED packages.

[0407] Please refer also the “GENERAL BACKGROUND” section at the top ofthe present specification, for additional remarks.

PRIOR ART

[0408] Please refer to Ref5 for any known prior art.

[0409] I have not found any additional information in these regards.

BACKGROUND

[0410] I had mentioned in my previous applications, especially in Ref3,as well as in Ref5, that “Oriented Leads or Columns” can improve thelife and reliability of plastic packages.

[0411] I had also shown a number of ways to achieve the desired designsand goals, mostly grouped under two methods.

[0412] A—Two-Step Method—Twist and Fold

[0413] In the two-step operation, the leg blanks exit in an “orthogonal”direction from the package body, i.e. in a direction that is “normal” or“perpendicular” to the body sides and/or axed. So, if we simply fold theleg blanks, then the vertical parts of the legs will also be“orthogonal”, hence not oriented as per invention. In order to get them“oriented” as required, we have to add a “twisting” operation. This wasall described at length in Ref3 and Ref5.

[0414] B—One:Step Method—Oriented Leg Blank with Fold Only

[0415] The other method was to use a flat leadframe with the leg blanksalready oriented and radiating directly from the plastic body already inthe proper direction, i.e. exiting already on an angle from the packagebody, i.e. on an angle to the package sides and axes. This allowed us tobe able to simply “fold” the leg blanks and through this one singleoperation, we were able to get the vertical part of the legs to be“oriented” as per recommendations of the invention.

[0416] This “one single step” folding operation compares favorablyagainst the other alternative, i.e. the “fold and twist” method. Thereasons are that it is a one-step operation only instead of a “two-step”operation, and where we need to also “twist” the legs to get them intothe proper “orientation”. The second reason is that twisting, if notdone properly and carefully, can overstress the plastic body or even thelegs material itself.

[0417] In Ref3 and Ref5, I had mentioned and described the “one-step”method, and have shown some figures illustrating the proposed method.Many of those figures were pretty small and it may have been toodifficult to recognize the fine details of the concept.

[0418] So, in this present application, I will show some figures, withmore details, to make sure that the concept is well understood.

[0419] I will also show another “one-step” method, which could beconsidered a compromise between method A and B. I will call this method,method C, the “Normal-Oriented” or “Orthogonal-Oriented” Leg Blank withFold Only” method. I will briefly describe it here, but I will, furtherbelow, show some figures to describe this method more filly in thesection on “DETAILED DESCRIPTION OF THE INVENTION—LEADED PRODUCTS”.

[0420] C-One-Step Method—“Orthogonal-Oriented” Leg Blank with Fold Only”Method.

[0421] In the two drawings attached to Ref6, FIG. 1 & 2, I showed aproposed way to create oriented leads out a flat leadframe. I will callthis method, method C, the “Orthogonal-Oriented” or “Normal-Oriented”Leg Blank with Fold Only” method. Compare this with the two othermethods, mentioned earlier above.

[0422] Here the portion of the leadframe that would generate eachindividual leg of the package, hereinafter referred to as “leg blank”,would be coming out of, or protruding from, or exiting from, the plasticbody will be orthogonal, i.e. perpendicular to the body's sides andcenterlines, the same way like the present conventional leadframes aremade today in the industry. However, the leg blanks would then beformed, or rather blanked, to radiate out in the proper desired orienteddirection, while they are still flat, as shown in the two figures. Thebig difference is that the portion of the leg blanks coming out of theplastic body would be orthogonal instead of on an angle. This makes iteasier to provide the “dams” that are necessary for the encapsulation ormolding process and then later to cut-off or trim the dams after theencapsulation or molding process is finished.

[0423] Objects

[0424] To enhance the reliability and to prolong the operating life ofleaded packages by reducing the stresses on the packages body; and alsoby reducing the stresses on the assemblies' solder joints and solderpads between the tips of the gull-wing legs of the packages and thesubstrates, on which the packages are mounted.

SUMMARY OF THE INVENTION

[0425] In this present invention, I will describe the third method offorming the legs of leaded packages, i.e. Method C, the“Normal-Oriented” Leg Blank with Fold Only” method.

[0426] I will also show some more examples of the second method, whichwas described in Ref3 and Ref5, i.e. Method B—One-Step Method—OrientedLeg Blank with Fold Only.

[0427] I will also show more figures describing the solder Dads thatwould accept the proposed oriented leads, especially the “combination”pads. These solder pads were also described in Ref3 and Ref5, but thepresent figures will give more details.

PAGES 117 THROUGH 120 LEFT OUT INTENTIONALLY DETAILED DESCRIPTION OF THEINVENTION—LEADED PRODUCTS

[0428] Review of Earlier Applications

[0429] First, let's refer to Ref5.

[0430] I will briefly review the drawings in that Ref5, which have somespecial relevance to the present specification.

[0431] Ref5, FIGS. 41 and 42 illustrate my definitions of “Fold” and“Twist”. Ref5, FIG. 41-B shows a “Twist” in a strip of sheet metal,which started “Flat”, and Ref5 FIG. 41-C shows a “Fold” in a similarstrip of sheet metal. Ref5, FIG. 42-D shows a progression from “Flat” to“Twist” and then to “Fold”. Ref5, FIG. 42-E reverses the order and showsa progression from “Flat” to “Fold” to “Twist”.

[0432] Ref5, FIGS. 2 and 3 show a (Prior Art) package with standardconventional legs. The leg blanks exit, or protrude from, the packagebody in a perpendicular direction to the sides and to the centerlines ofthe package. I refer to this condition as an “orthogonal” direction orsometimes as a “normal” direction. The leg blanks are later folded, tocreate the vertical parts of the legs, or “leg columns”. No twisting ofthe leg material is involved here.

[0433] Ref5, FIGS. 12 and 13 show an example of standard, conventionalflat leadframe. They also show the leg blanks are laid-out to beorthogonal, i.e. perpendicular to the sides and centerlines of theexpected body of the package.

[0434] Ref5, FIGS. 20 and 21 appear to have their leg blanks in anorthogonal direction as well. The two external leg blanks, at eitherside of the central one, are then folded at some angle, to create theoriented legs as shown.

[0435] Ref5, FIG. 22-A shows the legs, orthogonal and folded, but FIG.22-B shows the leg blanks oriented and folded.

[0436] Ref5, FIG. 23-C shows solder pads that are rectangular andoriented, in line with the thermal deformation rays. I will refer tosuch pads as “dedicated” solder pads. See more explanation later below.

[0437] Ref5, FIG. 23-D shows solder pads that can accept bothconventional gull-wing legs as well as oriented legs. I will refer tosuch pads as “combination” solder pads or simply “combo pads”. See moreexplanation later below.

[0438] Ref5, FIG. 25, top view shows the legs protruding from the bodyin an orthogonal direction, but bottom view shows them in a radial orrather oriented direction.

[0439] Ref5, FIG. 26 at first glance may look like Ref5, FIG. 21, butthere is a difference. Here the two external leg blanks seem to exitalready on an angle to the side of the package body. We can say thatthey are oriented already. The fold is orthogonal with the leg blank andat an angle to the package body.

[0440] Ref5, FIGS. 32 through 40 show oriented leg blanks. Suchleadframes will be referred to as “radial” or rather “oriented”leadframes. We only need to “fold” each leg blank orthogonally to thedirection of the leg blank itself and we would then get the verticalpart of each leg column oriented properly, as per present invention. Wedo not need to “twist” anything.

[0441] Ref5, FIGS. 32, 33, 35, 67 and 39 show the leadframe in its flatcondition. Ref5, FIGS. 34, 36, 38 and 40 after the leg blanks had beenfolded and automatically oriented.

[0442] Now, we'll review Ref6.

[0443] Ref6, FIG. 1 shows a flat leadframe, where the leg blanks exit orprotrude orthogonally, but then they curve around, while still in theflat leadframe condition, so that the following part of the leg blank,which would generate the vertical part of the legs, becomes oriented asrequired by the present invention. I will refer to that portion of theleg blank that curves around as the “neck” of the leg blank. Theincluded angle of each neck is different for each leg.

[0444] When we “fold” the leg blank, orthogonally, at the outer end ofthe neck, then the resulting vertical portion of the legs willautomatically be oriented properly, as per present invention.

[0445] Since each leg is supposed to be oriented at some respectiveproper angle, at its own respective angle with respect to the body'ssides or centerlines, then the included angle of each neck will also bedifferent for the different legs, to suit the requirements, as perpresent invention.

[0446] Ref6, FIG. 2 shows the leg blanks shown in Ref6, FIG. 1, butafter they have been “folded”, after each individual neck. We can seethat the vertical part of each leg is oriented properly, as per presentinvention.

[0447] Now, I will show and describe the new drawings.

[0448] I have used a standard, conventional package as a model for myexample. It is a “TSSOP” package. JEDEC (Joint Electronic DeviceEngineering Industry Development Association) defines TSSOP as “ThinShrink Small Outline Package”. I have used the package with twenty-eight(63) legs, i.e. seven (7) legs per quadrant.

[0449] This is just a model to demonstrate the concepts. The sameconcepts do apply to any other package, that has leads/legs, regardlessof size of package, number of legs, or whether the leads are on only twosides of the package or on all four sides, etc.

[0450] FIG. 36 shows the TSSOP (Prior Art) package, complete with bodyand legs, and ready to be assembled on a PCB or the like.

[0451] FIG. 37 shows the leadframe of the above package, without theplastic body or encapsulation. The leadframe is shown as if it hasalready gone through the manufacturing steps, i.e. encapsulation,de-damming, trimming/sizing and folding.

[0452] FIG. 38 shows a 3-D view of the whole leadframe, but in the flatcondition. This is the leadframe for only one package. Usually, thereare a number of such leadframes, all in a row, but I am showing only oneleadframe for one package only here.

[0453] FIG. 39 shows the same leadframe shown in FIG. 38, but in anorthogonal view.

[0454] FIG. 40 shows the same leadframe again, but it also shows thelocations of the solder pads, on the PCB, which will accept the tips ofthe package legs and get soldered to them.

[0455] FIG. 41 shows the same leadframe shown in FIG. 40, but with the“dams” trimmed off or “de-dammed”.

[0456] FIG. 42 shows the same leadframe shown in FIG. 41, but aftercutting or “sizing” the leg blanks to the proper length, so that theywould form the gull-wing tips of the legs.

[0457] FIGS. 43 and 44 show 3-D views of the package, with the gull-wingtips of the legs sitting on top of the solder pads. These are thestandard conventional solder pads.

[0458] All the above is “PRIOR ART”.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0459] Leadframe Embodiment #1

[0460] Now, I will describe a set of figures, showing a leadframeaccording to method B, the one-stop method of using “oriented legblanks”. See “Background” section.

[0461] Here the leg blanks protrude from, or exit, the package body onan angle with respect to the sides and centerlines of the package body.This permits that one folding operation would form the legs in theproper orientation.

[0462] Such an approach had already been described in Ref5. See FIGS. 32through 40. The following figures duplicate the concepts shown in thoseearlier figures, and show the concepts as applied to a real life model.

[0463] FIG. 45 shows the proposed leadframe, with the oriented legblanks. Please notice the differences between this leadframe and the oneshown in FIGS. 38 and 39. I will refer to such a leadframe as “oriented”leadframe or sometimes as “radiant” leadframe.

[0464] FIGS. 46 and 47 highlight those differences. FIG. 46 shows thewhole leadframe and FIG. 47 shows a part of one quadrant only. The new,oriented leadframe is designed to have all the features that areimportant in both leadframes. These features include 1) the platform tomount the chip, 2) the wire bonding pads, and 3) the location of themounting solder pads on the PCB. The new oriented leadframe satisfiesall these three requirements.

[0465] FIGS. 48 through 54 show the progression of steps to manufacturea package, using this oriented leadframe. As it can be seen, they arenot much different than with the standard conventional methods, exceptthat it starts with the oriented leadframe, and that the dams needs alsooriented tools to cut them off. Finally the folding tools will also haveto be oriented accordingly. A good toolmaker can make these toolsreadily.

[0466] FIG. 48 shows a 3-D view of the leadframe shown in FIG. 45.

[0467] FIG. 49 shows the bottom part of the package body, placed underthe leadframe. In reality the encapsulation process put the whole bodyon the leadframe in one shot, but I am showing it here in stages, justfor clarification.

[0468] FIG. 50 shows the middle part of the body in place.

[0469] FIG. 51 shows the whole body molded on the leadframe. Again, inreality, there are a few more steps that have not been shown here. Theyare the steps of attaching the chip to the leadframe and connecting itelectrically to the individual leg blanks. I am not proposing to changeany of those steps, so I did not see the need to get into those detailshere. I kept the figures to the bare minimum essentials, just forclarity.

[0470] FIG. 52 shows the leadframe after the “de-damming” operation.

[0471] FIG. 53 shows the leg blanks, after the “sizing” operation, wherethe leg blanks are trimmed to the proper length, in preparation for“folding”.

[0472] FIG. 54 shows the legs after the “folding” operation.

[0473] FIG. 54, together with FIGS. 55 through 58 show different viewsof the package after the legs have been folded to their final shape.

[0474] Note that the folding of the legs could be done at the same timeas the de-damming and the sizing/trimming operations. This is optional.

[0475] Note also that the folding of each leg would have to be at theproper orientation, as per present invention.

[0476] Finally, note also that up to this point, the package is stillattached to the carrier strip.

[0477] They will be separated from each other afterwards.

[0478] FIG. 59 shows an overview of the progression of the manufacturingsteps described above.

[0479] Solder Pads Embodiments

[0480] Once the package has been formed, as shown in FIGS. 54 through58, then we can mount the package on a PCB or the like, by soldering thetips of the gull-wing legs to some solder pads.

[0481] Here we have at least four different options or alternatives tochoose from.

[0482] 1. Use the standard conventional solder pads, as they are. Itwill be OK as will be seen below.

[0483] 2. Use round/circular or oblong/elliptical pads or the like. Thismay be questionable, but it sure is an alternative. I will not elaborateon this one, because it is easy to visualize.

[0484] 3. Use “dedicated” solder pads, which would be designedspecifically to accept these legs of the oriented legs packages. Thesepads could also accept the standard conventional packages, but it wouldbe better yet to go to alternative 3 below.

[0485] 4. Use “Combo” solder pads, which would be designed and optimizedto accept both kinds of packages, i.e. the standard conventionalpackages, as well as the “oriented legs” packages.

[0486] FIGS. 60 and 61 show the oriented leadframe, superimposed on topof the PCB solder pads. FIG. 60 is the counterpart of the leadframeshown in FIG. 40, where the leadframe dams are still in place. FIG. 61is the counterpart of the leadframe shown in L 41, after the dams havebeen removed.

[0487] FIG. 62 shows the standard conventional (Prior Art) “rectangular”solder pads, as specified by JEDEC. It is showing only the top rightquadrant of the leadframe. This is according to Alternative 1 above.

[0488] FIG. 63 shows the “dedicated” solder pads, as per presentinvention, as mentioned in Alternative 3 above.

[0489] FIG. 64 shows the preferred “combo” solder pads, as per presentinvention, which can work with both standard conventional packages, aswell as with the “oriented” packages, as proposed by the presentinvention.

[0490] There are several ways that we can use to arrive to the shape ofthese combo pads. I will not go into all these details here, because itcan take too much time. I will be happy to present the process to theExaminer, if desired. There are at least two main criteria to try tosatisfy, when designing such combo pads. First, try to provide thelargest surface possible to be soldered to the corresponding “foot” ofthe mating device, with at least enough surface for good solder fillets.This, however, has to be tempered by the available space on the PCB.Second, try to make sure that there are proper clearances between alladjacent pads and/or adjacent features on the PCB, to make sure thatthere will not be any electrical shorts between these features and/orthe pads themselves.

[0491] FIG. 65 shows an oriented package on top of dedicated pads.

[0492] FIG. 66 through 70 show another similar oriented package, butthis time, it is mounted on top of combo pads.

[0493] FIGS. 71 through 77 show a strange arrangement, just forclarification. Each figure shows both a standard leg and an oriented legsuperimposed on the same combo pad, each figure for one pad position ata time. This is simply to highlight the fact that both types of legswould work on these combo pads, as per present invention.

[0494] To make it easy to visualize, I have shown only one “padposition” at a time. For example, FIG. 71 shows the first pad above theshort centerline of the package. On top of this pad, I have shown thecorresponding leg of a standard package as well as the corresponding legof an oriented package. Similarly, FIG. 72 shows the second pad abovethe centerline, together with the two corresponding legs from a standardpackage and an oriented package. Again, FIG. 73 shows the third pad andthe two corresponding legs, etc., until FIG. 77, which shows the seventhpad and its two corresponding legs.

[0495] Leadframe Embodiment #2

[0496] Orthogonal & Oriented Leg Blanks

[0497] The following group of figures shows a new embodiment, which hasnot been shown previously, except in Ref6, FIGS. 1 and 2. The followingfigures will simply clarify the embodiment represented by these twoabove figures, showing more details thereof.

[0498] In the “BACKGROUND” section, I had mentioned three alternativemethods to achieve our objectives. Methods A, B and C.

[0499] I will elaborate here on Method C, which I referred to it as“Orthogonal-Oriented” Leg Blank with Fold Only.

[0500] Method C, the “Orthogonal-Oriented” Leg Blank with Fold Only”Method.

[0501] In the two drawings attached to Ref6, FIG. 1 & 2, I had shown aproposed way to create oriented leads out a flat leadframe. I will callthis method, method C, the “Orthogonal-Oriented” or “Normal-Oriented”Leg Blank with Fold Only” method. Compare this with the two othermethods, i.e. Methods A and B, mentioned earlier in the “Background”section.

[0502] In this method C, the portion of the leadframe that wouldgenerate each individual leg of the package, hereinafter referred to as“leg blank”, would be coming out of or protruding from, or exiting from,the plastic body will be orthogonal, i.e. perpendicular to the body'ssides and centerlines, the same way like the present conventionalleadframes are made today in the industry. However, the leg blanks wouldthen be formed, or rather blanked, to radiate out in the proper desiredoriented direction, while they are still flat, as shown in the twofigures. The big difference between this method and method B, is thatthe portion of the leg blanks coming out of the plastic body would beorthogonal instead of on an angle. This makes it easier to provide the“dams” that are necessary for the encapsulation or molding process andthen later to cut-off or trim the dams after the encapsulation ormolding process is finished.

[0503] The following figures will show this proposed method C.

[0504] The major difference between the embodiment #2 and the previousone, is the way the leg blanks are formed or rather “blanked”.

[0505] There is another difference also between this following group offigures and the earlier ones. It is the ending or termination of thelegs. The earlier figures showed the legs endings shaped in a gull-wingsform, so that they can be surface mounted to pads on a PCB. In thesecond group of figures, the legs are terminated with solder tails,which would be inserted into “through-holes” in a PCB, for clinchingand/or soldering. Both endings can be used in either of the twoembodiments. I chose one ending/termination for one embodiment andanother ending/termination for the second, just for illustrationpurposes.

[0506] FIGS. 78 through 81 show four different views of the package asproposed by the present invention embodiment. FIG. 78 shows a 3-D viewof the package, FIG. 79 shows a top view, FIG. 80 shows a side view andFIG. 81 shows an end view.

[0507] These four figures show that all the legs first protrude out fromthe package body in an orthogonal direction, i.e. perpendicular ornormal to the body's sides and long centerline. We will refer to thatportion of the legs as the base (1). See FIG. 78. However, after acertain distance along the base in that orthogonal direction, we see a“neck” (2) in each leg. The neck of each leg, in any one quadrant, isdifferent than the necks in the adjacent legs. The neck encompasses acertain included angle (7). The neck ends up at a point, where the legblank becomes straight again. We will refer to the first portion of thisstraight run as the shoulder (3). Then the leg blank is folded to createthe vertical portion of the leg. The portion that is folded will bereferred to as the “fold” (4). The subsequent vertical portion consistsof at least the two following portions. First, the column (5) and thenthe solder tail (6). The shoulder makes a certain angle (7) with respectto the long axis (9) of the package body.

[0508] FIG. 82 shows a 3-D view of the package, with the solder tails ofeach leg inserted in the respective solder through-hole of a PCB.

[0509] FIG. 83 shows one side of the same package with the solder tailsinserted in the through-holes. The PCB in this figure is shown as if itsemi-transparent.

[0510] FIG. 84 shows the blank leadframe, which would be used to makethe above package. This is the counterpart of the leadframes shown inFIGS. 45 or 48, which were to be used for method B.

[0511]FIG. 85 shows a 3-D view of the leadframe shown in FIG. 84.

[0512] FIG. 86 shows the leadframe shown in FIGS. 84 and 85, but withthe package body already on it. The dams are still in place.

[0513] FIG. 87 shows the dams cut-off and removed.

[0514] FIGS. 88 and 89 show 3-D views of the above leadframe, with thepackage on it.

[0515] FIG. 90 shows the same thing, but after folding the legs, but itis still on the carrier strip.

[0516] FIG. 91 shows a top down view of the leadframe shown in FIG. 90,but without the package body.

[0517] FIG. 92 shows just the leadframe after all the trimming andfolding operations, but again without the package body. This is just forvisualization.

1. A solder pad, hereafter referred to as pad, similar to those solderdads that are used to mount electrical or electronic components ordevices, hereinafter referred to as device(s), onto substrates orprinted circuit boards, hereinafter referred to as PCB(s), wherein a)said pad is formed in a certain shape, so as to control the shape andcross-section of the solder connection or solder joint that will beformed on top of it, between said device pad and said PCB pad.
 2. Pads,as in claim 1, wherein a) said pad on the PCB, hereinafter referred toas PCB pad, and its corresponding pad on the device, hereinafterreferred to as device pad, both have a similar shape, to make a “matchedpair or a matched set of pads”.
 3. Pads, as in claim 1, wherein a) saidpad on the PCB (PCB pad) and its corresponding pad on the device (devicepad), both are elongated, i.e. the pad length is larger than the padwidth, in order to get the solder joint to have an elongatedcross-section as well, i.e. the length of said joint cross-section wouldbe larger than the width of said joint cross-section.
 4. A pad, as inclaim 2, wherein a) both said two pads of said matched pair or a matchedset are oriented in the same direction, i.e. the long axis of said PCBpad is in the same direction as the long axis of said device pad, andsimilarly the short axis of said PCB pad is in the same direction as theshort axis of said device pad.
 5. A pad as in claim 3, wherein a) saidshort axis of each one of said two pads is in line with a thermaldeformation ray, which would start at the thermal center or the fixationpoint of said device and would emanate towards the center of said pads.6. A pad, as in claim 5, wherein a) said short axis of each one of saidtwo pads is approximately in line with a ray, which would start at thethermal center or the fixed point of the device and would emanatetowards the center of said pad, and could be within a few degrees offfrom said ray.
 7. A solder joint, joining pads on a PCB and pads on adevice, wherein a) said joint has an elongated cross-section, wherebyone main axis of said cross section is longer than the second axis ofsaid cross section, and whereby said long and said short axes areapprox. perpendicular to each other.
 8. A solder joint as in claim 7,whereby a) said solder joint is oriented such that said short axis ofsaid joint cross section is approximately in line with the thermaldeformation ray emanating from the thermal center of said device or fromthe fixation point of said device, and reaching towards the geometriccenter of said solder joint cross section.
 9. A solder joint as in claim7, whereby a) said solder joint has an approximately uniformcross-section along its entire height, except at the bases where theremay be a fillet, to look like a uniform cross-section solder column. 10.A solder joint as in claim 7, whereby a) said solder joint has a smallercross-section at about the middle of its height, than the cross-sectionnear its bases, which are near the device pad or near the PCB pad.
 11. Asolder joint as in claim 7, whereby a) said solder joint has a smallercross-section at about the middle of its height, than the cross-sectionnear its bases, which are near said device pad or near said PCB pad,i.e. like an hour-glass shape or a Mae West shape.
 12. A Method ofcreating an assembly, where said assembly consists of a device attachedto a PCB by a joining means where said means is attached to joining padson said device and said PCB, whereby a) a spacer is introduced betweensaid device and said PCB, to control the distance between said deviceand said PCB.
 13. An assembly, as in claim 12, whereby a) said spacer isa part of said joining means.
 14. An assembly, as in claim 12, wherebya) said spacer is not a part of said joining means.
 15. An assembly, asin claim 12, whereby a) said spacer changes its size during the assemblyprocess.
 16. An assembly, as in claim 15, whereby a) said change in sizeof said spacer is non-linear.
 17. An assembly, as in claim 15, wherebya) said change in size of said spacer is achieved through an externalmeans.
 18. An assembly, as in claim 15, whereby a) said change in sizeof said spacer is achieved by controlling and changing its temperatureduring the assembly process.
 19. An assembly, as in claim 12, whereby a)said joining means is a solder joint.
 20. A leadframe blank, to be usedin creating a leaded electronic package having more than one leg,whereby, a) said leadframe blank in its flat unfolded form, has each legblank, which will create the individual legs of said package, orientedalong its respective thermal deformation ray, wherein each said raystarts at or near the thermal center of the said package, and emanatesin the direction going towards the geometric center of said leg columncross-section, or towards the axis of said leg column, after said legblank would have been folded to create said leg column into its workingshape and position.
 21. A leadframe blank, as in claim 20, whereby b)said leg blank starts near the outline of said package in a directionthat is normal to the sides or centerlines of said outline of saidpackage and then, while said blank is still flat, said leg blank curvesat its neck and then the subsequent portion of said leg blank continuesin a direction of its respective thermal deformation ray, wherein saidray starts at or near the thermal center or fixation point of saidpackage, and emanates in the direction going towards the geometriccenter of said leg column cross-section, or towards the axis of said legcolumn, after said leg blank would have been folded to create said legcolumn into its working shape and position.